EE104x

Question 1

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Question text

To test the accuracy of a kilowatt-hour meter an

electrician used a wattmeter. He found out that the

meter makes 5 revolutions in 18 seconds. The meter

constant is 3.2. What is the percentage error if the

wattmeter reading is 3368?

Select one:

a. 8% slower

b. 5% faster

c. 5% slower

d. 8% faster

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The correct answer is: 5% slower

Question 2

Incorrect



Question text

A magnetomotive force is supplied by a current of one

ampere through 100 turns. The magnetic circuit

consists of a steel core of 1000 permeability, 10 cm

long and 4 sq. cm area and an air gap one cm long.

What is the field intensity at the air gap?

Select one:

a. 100.53 oersted

b. 12.25 oersted

c. 497.66 oersted Incorrect

d. 124.4 oersted

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The correct answer is: 124.4 oersted

Question 3

Correct



Question text

A parallel plate capacitor is made of 350 plates,

separated by paraffin paper 0.0010 cm thick (k = 2.5).

The effective size of plate is 15 by 30 cm. What is the

capacitance of this capacitor?

Select one:

a. 140 uF

b. 70 uF

c. 15 uF

d. 35 uF

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The correct answer is: 35 uF

Question 4

Incorrect



Question text

To double the current range of a 50-micro-amp, 2 kilo-

ohm moving coil meter movement, the shunt

resistance should be

Select one:

a. 2 kilo-ohms

b. 1 kilo-ohm

c. 18 kilo-ohms Incorrect

d. 50 kilo-ohms

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The correct answer is: 2 kilo-ohms

Question 5

Correct



Question text

If an alternating voltage has a magnitude of 10 V at

30 degrees, what is its maximum voltage?

Select one:

a. 30 V

b. 40 V

c. 50 V

d. 20 V

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The correct answer is: 20 V

Question 6

Correct



Question text

A wire carries a current i = 3 cos 314t amperes. What

is the average current over 6 seconds?

Select one:

a. 0 A

b. 3.0 A

c. 0.532 A

d. 1.5 A

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The correct answer is: 0 A

Question 7

Correct



Question text

What is the flux density having a flux of 12,000

maxwells through a perpendicular area of 6 cm

squared?

Select one:

a. 2,000 gauss

b. 200 gauss

c. 72,000 gauss

d. 72 gauss

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The correct answer is: 2,000 gauss

Question 8

Correct



Question text

The result of capacitance C1 = 6 microfarads and C2

connected in series is 3 microfarads. Capacitor C2, in

microfarads is

Select one:

a. 3

b. 6

c. 8

d. 4

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The correct answer is: 6

Question 9

Correct



Question text

MERALCO used two wattmeters to measure the

balanced 3-phase dynatron elevator motor drive. The

coils of the wattmeters are connected to the current

transformers, which are lines 1 and 2 respectively.

The potential coils are connected to potential

transformers, which are across lines 2 and 3 and lines

3 and 1, respectively. The line potentials are 230 V

and the line currents are each 150 A. The wattmeters

each indicate 19.6 kW. Assume load is wye

connected. What is the total power supplied?

Select one:

a. 45.461 kW

b. 49.175 kW

c. 47.350 kW

d. 48.236 kW

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The correct answer is: 49.175 kW

Question 10

Not answered

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Question text

The torque of a spring controlled ammeter varies as

the square of the current thru it. If the current of 5

amperes produces deflection of 90 degrees, the

deflection in degrees for a current of 3 amperes is

____.

Select one:

a. 18

b. 32.4

c. 30

d. 54

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The correct answer is: 32.4

Question 11

Incorrect



Question text

A galvanometer has a resistance of 300 ohms. What

is the ohmic resistance to make it read one is to ten?

Select one:

a. 33.33

b. 30 Incorrect

c. 10

d. 100

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Question 12

Correct



Question text

Solenoid 25 cm long is wound with 200 turns, what is

the value of the field strength inside the solenoid,

when carrying a current of 2 amperes.

Select one:

a. 1000 AT/m

b. 1600 AT/m

c. 1400 AT/m

d. 1200 AT/m

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The correct answer is: 1600 AT/m

Question 13

Correct



Question text

If three 100-pf capacitors are connected in series,

then the total capacitance is

Select one:

a. 300 pF

b. 50 pF

c. 33.3 pF

d. 100 pF

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The correct answer is: 33.3 pF

Question 14

Correct



Question text

A sinusoidal voltage wave has an RMS value of 70.71

V and a frequency of 60 Hz. Determine the value of

the voltage 0.0014 second after the wave crosses the

wt axis.

Select one:

a. 70.71 V

b. 100 V

c. 50 V

d. 141.42 V

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Question 15

Incorrect



Question text

A 12 micro-farad capacitor charged at 500 Volts and a

6 micro-farad capacitor charged at 250 Volts are

connected in parallel. What is the potential difference

in the combination?

Select one:

a. 750 Volts Incorrect

b. 417 Volts

c. 500 Volts

d. 450 Volts

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The correct answer is: 500 Volts

Question 16

Correct



Question text

How long can a battery last with capacity of 50

ampere-hour running equipment of 5 amperes?

Select one:

a. 10 hours

b. 250 hours

c. 100 hours

d. 25 hours

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The correct answer is: 10 hours

Question 17

Correct



Question text

Two coils of inductances 4 H and 6 H are connected

in parallel such that their mutual inductance is 3 H

assists the self-inductance. The total inductance of

the combination is ____.

Select one:

a. 8.25 H

b. 2.06 H

c. 3.75 H

d. 0.94 H

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The correct answer is: 3.75 H

Question 18

Incorrect



Question text

Two parallel wires 10 cm apart carry current in the

opposite direction of 8 A. What is the magnetic field

halfway between them?

Select one:

a. 32 x 10^-6 T

b. 16 x 10^-6 T Incorrect

c. 8 x 10^-6 T

d. 64 x 10^-6 T

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The correct answer is: 64 x 10^-6 T

Question 19

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Question text

Two similar poles, each of 1 Wb, placed 1 m apart in

air will experience a repulsive force of

Select one:

a. 796 kN

b. 63 x 10^-3 N

c. 63000 N

d. 8 x 10^12 N

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The correct answer is: 63000 N

Question 20

Correct



Question text

If a body is considered as a conducting sphere of 0.5

m radius, its capacitance to infinity is

Select one:

a. 55 nF

b. 55 uF

c. 55 pF

d. 55 F

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The correct answer is: 55 pF

Question 21

Correct



Question text

A certain electric welder has a basic circuit equivalent

to a series RL with R = 0.1 ohm and L = 1 mH. It is

connected to an AC source e through a switch s

operated by an automatic timer, which closes the

circuit at any desired point on the 60 cycle, sinusoidal

wave e. Calculate the magnitude of the transient

current resulting when s closes as e is passing

through its peak value of 100 volts.

Select one:

a. 256.41 A

b. 76.32 A

c. 65.74 A

d. 80.54 A

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The correct answer is: 65.74 A

Question 22

Not answered

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Question text

A 1% d Arsonval meter movement has coil and

swamping resistance adding to 200 ohms. The full-

scale voltage is 50 mV. Determine the shunt

resistance required producing 1 A full scale current

meter.

Select one:

a. 48.74 milli-ohms

b. 49.22 milli-ohms

c. 50.01 milli-ohms

d. 52.02 milli-ohms

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The correct answer is: 50.01 milli-ohms

Question 23

Correct



Question text

In symmetrical components, what is the vector sum of

1 + a + a^2?

Select one:

a. infinity

b. -1

c. 0

d. 1

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Question 24

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Question text

A 35 unit south pole is placed 1 inch to a 20 unit south

pole. Determine the force between the poles.

Select one:

a. 129.5, repulsion

b. 129.5, attraction

c. 108.5, attraction

d. 108.5, repulsion

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The correct answer is: 108.5, repulsion

Question 25

Incorrect



Question text

Twenty-four (24) dry cells are arranged in rows of six

(6) in series and the four (4) rows in parallel. The emf

of each cell is 1.40 Volt, and internal resistance of

each is 0.08 ohm. Determine the current to an

external resistor of 3.2 ohms.

Select one:

a. 2.53 A

b. 5.23 A

c. 5.32 A

d. 2.35 A

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Question 26

Correct



Question text

In an RL circuit, Kirchhoff law gives the following

relation: E = Ldi/dt + Ri where: E = supply voltage

(200 volts), R = resistance (20 ohms), L = inductance

(1 Henry), t = time in seconds, i = current in amperes.

If i = 0 when t = 0, find i when t = 0.02 second.

Select one:

a. 3.3 A

b. 3.2 A

c. 3.1 A

d. 3.0 A

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Question 27

Correct



Question text

An electric heater carries 12 A at 110 V, is submerged

in 22.5 lbs of water for 30 minutes. What will be the

final temperature of the water if its initial temperature

is 35 degrees F?

Select one:

a. 133.56 degrees F

b. 135.43 degrees F

c. 125.42 degrees F

d. 128.33 degrees F

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The correct answer is: 135.43 degrees F

Question 28

Correct



Question text

A 6.0 H coil whose resistance is 12 ohms is

connected in series with a 24 ohms resistor and to a

144 V battery and a switch. The switch is closed at t =

0. Determine the energy stored in the magnetic field

at steady state.

Select one:

a. 46 J

b. 50 J

c. 52 J

d. 48 J

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The correct answer is: 48 J

Question 29

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Question text

A coil has 2500 turns and a current of 10 A flowing in

it produces an effective flux of 0.05 Weber. If the

resistance is 12 ohm, what is the time constant of the

coil

Select one:

a. 1.12 sec

b. 2.25 sec

c. 1.0 sec

d. 0.75 sec

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The correct answer is: 1.12 sec

Question 30

Correct



Question text

What is the size in square millimeter (mm^2) is the

cable of 250 MCM size?

Select one:

a. 126.675 mm^2

b. 132.348 mm^2

c. 118.656 mm^2

d. 112.565 mm^2

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The correct answer is: 126.675 mm^2

Question 31

Correct



Question text

An analog ohmmeter reads 18 on R X 10 k range.

What is the value of the measured resistance?

Select one:

a. 18 ohms

b. 18 kilo-ohms

c. 180 ohms

d. 180 kilo-ohms

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Question 32

Correct



Question text

An inductor draws 5 A of current at 110 volts, 60 Hz.

Determine the inductance.

Select one:

a. 56.38 mH

b. 58.36 mH

c. 38.56 mH

d. 53.68 mH

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The correct answer is: 58.36 mH

Question 33

Correct



Question text

If a force of 4.8 x 10^(-2) N is required to move a 40

uC charge in an electric field between two points 20

cm apart. What is the potential difference between

two points?

Select one:

a. 240 Volts

b. 360 Volts

c. 120 Volts

d. 160 Volts

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Question 34

Correct



Question text

Three resistors 10, 15 and 30 ohmic values are

connected in wye-configuration to a balanced 208 volt

three-phase supply. Calculate the total power of the

system.

Select one:

a. 2880 W

b. 3280 W

c. 3080 W

d. 2644 W

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The correct answer is: 2644 W

Question 35

Correct



Question text

A DC voltage of 80 volts is applied to a circuit

containing a resistance of 80 ohms in series with an

inductance of 20 Henry. Calculate the growth of

current at the instant of completing the circuit.

Select one:

a. 2 A/s

b. 1/4 A/s

c. 1/2 A/s

d. 4 A/s

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The correct answer is: 4 A/s

Question 36

Correct



Question text

Twelve similar wires each of resistance 2 ohms are

connected so as to form a cube. Find the resistance

between the two corners of the same edge.

Select one:

a. 1.167 ohms

b. 1.133 ohms

c. 1.102 ohms

d. 1.125 ohms

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The correct answer is: 1.167 ohms

Question 37

Correct



Question text

Determine the rms value of a semi-circular current

wave which has a maximum value of A.

Select one:

a. 0.23 A

b. 0.816A

c. 0.707A

d. 0.866A

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The correct answer is: 0.816A

Question 38

Correct



Question text

A current of 10 amperes at a power factor of 0.8

lagging is taken from 250 V a.c. supply. The reactive

power of the system is

Select one:

a. 1500 VAR

b. 2000 VA

c. 1500 watts

d. 2000 watts

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The correct answer is: 1500 VAR

Question 39

Not answered

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What is the coefficient of coupling of two coils whose

mutual inductance is 1 H and whose self-inductances

are 1.2 and 2 H?

Select one:

a. 0.645

b. 0.912

c. 2.400

d. 1.549

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Question 40

Not answered

Marked out of 1.00


Question text

A magnetic coil produces 100,000 Maxwell with 2,000

turns and with a current of 2 A. The voltage is cut-off

and the flux collapses in 0.01 sec. What is the

average voltage that will appear across the coil?

Select one:

a. 20 kV

b. 2,000 kV

c. 2 kV

d. 200 V

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Question 41

Correct



Question text

A current transformer has a single turn primary and a

200 turn secondary and is used to measure a.c.

current with the help of a standard 5-A a.c. ammeter.

These arrangements can measure a line current of up

to ____ ampere,

Select one:

a. 40

b. 200

c. 1000

d. 5000

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Question 42

Incorrect



Question text

The stator of a 440 V, 50 HP shunt motor is tested at

75 degrees C for its insulation resistance between

terminals connected together and the ground frame.

When a 50,000 ohm voltmeter is connected in series

with a 600 V DC source, the meter indicates 125 V.

Calculate the insulation resistance.

Select one:

a. 190 kilo-ohms

b. 170 kilo-ohms

c. 200 kilo-ohms

d. 180 kilo-ohms Incorrect

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Question 43

Correct



Question text

An ammeter has a range of 0 - 10 amps. What is

shunt resistance to be connected if the range is

increased to 100 amps? The internal resistance of the

ammeter is 0.10 ohms.

Select one:

a. 2.111 ohms

b. 0.0111 ohms

c. 0.111 ohms

d. 1.111 ohms

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Question 44

Correct



Question text

A circuit draws 25 A when connected across a source

of frequency f1. Determine the current drawn by the

same circuit at resonance if f1 is half the resonant

frequency.

Select one:

a. 12.5 A

b. 50 A

c. 35.35 A

d. 17.68 A

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Question 45

Correct



Question text

A generator has a field winding with an inductance L =

10 Henry and a resistance Rf = 0.1 ohm. To break the

initial field current of 1000 amperes, the field breaker

inserts a field discharge resistance Rd across the field

terminals before the main contacts open. As a result,

the field current decays to zero according to the

differential equation. L*di/dt + i*R = 0, Where: R = Rf

+ Rd preventing a sudden decrease of i to zero, and a

resulting high inductive voltage due to L. Solve the

differential equation and determine the value of Rd

that would limit the initial voltage across it to 1,000

volts

Select one:

a. 0.95 ohm

b. 0.90 ohm

c. 0.85 ohm

d. 0.80 ohm

Feedback

The correct answer is: 0.90 ohm

Question 46

Incorrect



Question text

A capacitor is charged with 0.23 watt-second of

energy at a voltage of 48 volts. What is its

capacitance?

Select one:

a. 220 uF

b. 180 uF

c. 240 uF Incorrect

d. 200 uF

Feedbacks


Question 47

Correct



Question text

A magnet which generates 800 Maxwell of flux, is

inserted through a coil of 1000 turns. It is then

withdrawn within 0.15 sec. What is the voltage that

appears across the coil?

Select one:

a. 0.22 V

b. 533 V

c. 0.0533 V

d. 53.3 V

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The correct answer is: 0.0533 V

Question 48

Incorrect



Question text

Find the capacitance of a two plate capacitor of plate

area 12 sq. inch dielectric constant of 6 and dielectric

thickness of 0.01 inch.

Select one:

a. 1.6 nF

b. 1.5 nF

c. 1.2 nF Incorrect

d. 1.3 nF

Feedback

The correct answer is: 1.6 nF

Question 49

Incorrect



Question text

Four capacitors A, B, C and D are connected across a

15-V DC source. The charges accumulated in A, B

and C are equal to 2000, 750 and 1500 uC,

respectively. If the total capacitance of the

combination is known to be 35 uF, how much charge

is accumulated in capacitor D?

Select one:

a. 1000 uC

b. 1400 uC

c. 1200 uC Incorrect

d. 1500 uC

Feedback

The correct answer is: 1000 uC

Question 50

Incorrect



Question text

A power plant customer draws power at 220 volts

from transformers on a pole. Current transformers

with a ratio of 200/5 are used to meter the electrical

usage. What is the multiplier of the kW-hr and

demand meters?

Select one:

a. 40

b. 100

c. 200 Incorrect

d. 80

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A magnetic pole produces 5000 field lines. How much is the flux in Weber?

Select one:

a. 50 x 10^-6

b. 5 x 10^-6

c. 500 x 10^-5

d. 500 x 10^-6

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The correct answer is: 50 x 10^-6

The field winding of a DC generator is wound with 900 turns and has a resistance of 50 ohms. If the

winding is excited from a 240 V dc source, the magnetic flux linking the coil is 4 mWb. Determine the self-

inductance of the coil.

Select one:

a. 0.56 H

b. 0.83 H

c. 0.92 H

d. 0.75 H

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A copper disc of radius 0.1m is rotated about its centre with 20 revolutions per second in a uniform

magnetic field of 0.1 T with its plane perpendicular to the field. The emf induced across the radius of the

disc is

Select one:

a. 20pi millivolt

b. pi/10 volt

c. pi/20 volt

d. 10pi millivolt

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The correct answer is: 20pi millivolt

Twelve similar wires each of resistance 2 ohms are connected so as to form a cube. Find the resistance

between the two diagonally opposite corners.

Select one:

a. 1.28 ohms

b. 1.45 ohms

c. 1.66 ohms

d. 2.01 ohms

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The field winding of a separately-excited DC generator has an inductance of 60 H and a resistance of 30

ohms. The discharge resistance of 50 ohms is permanently connected in parallel with winding which is

excited from a 200 volt supply. Find the value of the decay current 0.60 sec after the supply has been

switched off.

Select one:

a. 1.12 A

b. 3.67 A

c. 3 A

d. 4.94 A

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Three 3.33 ohms resistors are connected in wye. What is the value of the equivalent resistors connected

in delta?

Select one:

a. 20 ohms

b. 10 ohms

c. 3.33 ohms

d. 6.67 ohms

Feedback

The correct answer is: 10 ohms

Two capacitors 30 and 10 microfarad are connected in series, what is the total capacitance?

Select one:

a. 20 microfarad

b. 7.5 microfarad

c. 300 microfarad

d. 40 microfarad

Feedback

The correct answer is: 7.5 microfarad

In a test of a 10-ampere watthour meter having a constant of 0.40, the disk makes 40 revolutions in 55

seconds. The average volts and amperes during this period are 116 volts and 10 amps. Determine the

percent accuracy of this meter at this load.

Select one:

a. 91.03%

b. 83.46%

c. 90.28%

d. 92.34%

Feedback

The correct answer is: 90.28%

A generator supplies three-phase power to balanced load. The voltage is 230 volts, the current is 18 A

and the power factor is 85%. What is the power?

Select one:

a. 3.6 kW

b. 1.4 kW

c. 1.6 kW

d. 6.1 kW

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A certain 50 micro-A meter movement has a resistance of 90 ohms. What value of series multiplier is

needed to make an instrument that will read 5 volts (maximum)?

Select one:

a. 102 kilo-ohms

b. 110 kilo-ohms

c. 98 kilo-ohms

d. 99.91 kilo-ohms

Feedback

The correct answer is: 99.91 kilo-ohms

A voltage rise linearly from zero to 100 volts in 1 second, falls instantaneously to zero at t = 1 second and

remains zero thereafter. This voltage is applied to an RL series circuit in which R = 5 ohms and L = 100

mH. What is the current when t = 0.50 second?

Select one:

a. 9.60 A

b. 69 A

c. 6.90 A

d. 96 A

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The following are in series R = 1,000 ohms, L = 100 uH and C = 20,000 pF. The voltage across the circuit

is 100 V, 60 kHz. What is the total impedance expressed in ohms?

Select one:

a. 1885 ohms

b. 1882 ohms

c. 2132 ohms

d. 1000 ohms

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If an oscilloscope with a vertical deflection of 0.1 volt rms per centimeter (cm), is used in conjunction with

a 10 ohm shunt resistor to measure a 25 milli-amp current, compute the vertical deflection?

Select one:

a. 0.025 cm

b. 0.25 cm

c. 2.5 cm

d. 25 cm

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The correct answer is: 2.5 cm

Two equal resistances are connected in series across a certain supply. If the resistances are now

connected in parallel across the same supply, the power produced will be ____ that of series connection.

Select one:

a. four times

b. two times

c. one-fourth

d. one-half

Feedback

The correct answer is: four times

Three equal positive charges of 10 statcoulomb each are located at the vertices of an equilateral triangle

of 2 cm leg. What is the magnitude of the force acting on each charge?

Select one:

a. 12.5 dynes

b. 50 dynes

c. 43.3 dynes

d. 25 dynes

Feedback

The correct answer is: 43.3 dynes

A star-connected 400 HP (metric), 2000 V, 50 c/s motor works at a power factor of 0.7 lagging. A bank of

mesh-connected condensers is used to raise the power factor to 0.93 lagging. Calculate the capacitance

of each unit required if each is rated 500 V, 50 c/s. The motor efficiency is 85%.

Select one:

a. 302 uF

b. 225 uF

c. 194 uF

d. 233 uF

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A three-phase induction motor delivers 150 HP while operating at 80% efficiency and a power factor of

0.8 lagging from 480 V lines. A wye connected power factor correction capacitor is to be installed to

improve the overall power factor to 0.9 lagging. Determine the capacitance required per phase.

Select one:

a. 3850 uF

b. 1283 uF

c. 428 uF

d. 142.6 uF

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A 120 cm long conductor is carrying a current of 1.2 amperes and is situated at right angles to the field to

flux density of 0.65 Tesla. Calculate the force on the conductor.

Select one:

a. 1.587 N

b. 0.936 N

c. 1.348 N

d. 3.264 N

Feedback

The correct answer is: 1.587 N

Two point charges Q1 = 50 microcoulombs and Q2 = 10 microcoulombs are located at (-1, 1, 3) and (3, 1,

0) meters respectively. Find the magnitude of the force on Q1.

Select one:

a. 0.018 N

b. 4.9 N

c. 124.5 N

d. 74 N

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A magnetic circuit consists of silicon steel of 2000 permeability of 10 cm length and cross sectional area

of 22 sq cm and an air gap of the same cross section area and of 1 cm length. A one ampere current

flows through 500 turns of coil. Calculate the field intensity across the gap.

Select one:

a. 350 Oersted

b. 590 Oersted

c. 755 Oersted

d. 622 Oersted

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The correct answer is: 622 Oersted

A single phase circuit is supplied from a 220 volts 60 Hz source draws 2000 watts of power and 10

amperes current. What is the power factor of the circuit?

Select one:

a. 90.9%

b. 100%

c. 82.6%

d. 72.5%

Feedback

The correct answer is: 90.9%

A voltmeter using a 20 micro-amp meter movement has an ohm/V rating of

Select one:

a. 1 kilo-ohm/V

b. 10 mega-ohms/V

c. 50 kilo-ohms/V

d. 20 kilo-ohms/V

Feedback

The correct answer is: 50 kilo-ohms/V

The torque of a spring controlled ammeter varies as the square of the current thru it. If the current of 5

amperes produces deflection of 90 degrees, the deflection in degrees for a current of 3 amperes is ____.

Select one:

a. 18

b. 30

c. 54

d. 32.4

Feedback


Three (3) 10-uF capacitors are connected in series. What is the total capacitance?

Select one:

a. 60 uF

b. 6.66 uF

c. 3.33 uF

d. 30 uF

Feedback

The correct answer is: 3.33 uF

Three impedances Za, Zb and Zc are connected in parallel. If at 60 Hz, Za = j8, Zb = -j2 and Zc = 5 ohms.

Solve for the resultant power factor.

Select one:

a. 0.573 leading

b. 0.471 leading

c. 0.471 lagging

d. 0.573 lagging

Feedback

The correct answer is: 0.471 leading

Copper wire of certain length and resistance is drawn out to four times its length without change in

volume. What is the resistance of the bar?

Select one:

a. 16R

b. unchanged

c. R/16

d. 4R

Feedback

The correct answer is: 16R

An ammeter rated 5 A, having a resistance of 0.5 ohm, is to be converted into a 200-V voltmeter by

connecting a resistor in series with the ammeter. Calculate the value of this resistance.

Select one:

a. 37.4 ohms

b. 39.5 ohms

c. 35.5 ohms

d. 34.6 ohms

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To roughly check his kWh meter an electrician hook-up a wattmeter, he switched on the load, he counted

5 rev in 18 sec, the meter constant is 3.2. The wattmeter reads 368 Watts. What is the error of the meter?

Select one:

a. 8% slower

b. 5% slower

c. 5% faster

d. 8% faster

Feedback


A 12 micro-farad capacitor charged at 500 Volts and a 6 micro-farad capacitor charged at 250 Volts are

connected in parallel. What is the potential difference in the combination?

Select one:

a. 450 Volts

b. 750 Volts

c. 417 Volts

d. 500 Volts

Feedback


An inductive coil having a resistance of 25 ohms and inductance of 0.2 H is connected in parallel with a

100 uF capacitor. Find the frequency at which the total current taken is in phase with the supply voltage.

Select one:

a. 29.5 Hz

b. 52.9 Hz

c. 46.5 Hz

d. 35.6 Hz

Feedback

The correct answer is: 29.5 Hz

An ammeter has a range of 0 - 10 amps. What is shunt resistance to be connected if the range is

increased to 100 amps? The internal resistance of the ammeter is 0.10 ohms.

Select one:

a. 0.111 ohms

b. 0.0111 ohms

c. 2.111 ohms

d. 1.111 ohms

Feedback


Four cubic meters of water is to be heated by means of four 1.5 kW, 230-V immersion heating elements.

Assuming the efficiency of the heater as 90%, determine the time required in boiling the water if the initial

temperature is 20 degrees C and if all four elements are connected in parallel.

Select one:

a. 69 hrs

b. 71 hrs

c. 66 hrs

d. 63 hrs

Feedback

The correct answer is: 69 hrs

A DC electromagnet is wound with 1000 turns of wire having a resistance of 30 ohms. When excited by a

voltage of 125 V, a magnetic flux of 2 mWb links the coil. What is the energy stored in the magnetic field?

Select one:

a. 8.34 J

b. 0.96 J

c. 4.17 J

d. 0.48 J

Feedback

The correct answer is: 0.48 J

A core of annealed steel sheet is wound with 1500 turns to wire through which a current of 40 mA is

flowing. If the length of the coil is 20 cm, calculate the magnetic strength is Amp-turns per meter.

Select one:

a. 350

b. 300

c. 450

d. 400

Feedback


How much time is required for electromagnetic energy to travel one nautical mile and return to the

source?

Select one:

a. 12.36 microseconds

b. 24.72 microseconds

c. 6.18 microseconds

d. 18.54 microseconds

Feedback

The correct answer is: 12.36 microseconds

Calculate the magnitude of the electric field at a point that is 30 cm from a point charge Q = -3.2 x 10^-6

C.

Select one:

a. 2.8 x 10^6 N/C

b. 3.2 x 10^6 N/C

c. 3.0 x 10^5 N/C

d. 2.4 x 10^5 N/C

Feedback

The correct answer is: 3.0 x 10^5 N/C

Four 3 pCoul spheres are in corners of square q 1 cm on sides. Find the force in Newton?

Select one:

a. 15.5 x 10^(-10)

b. 4.05 x 10^(-10)

c. 20.25 x 10^(-10)

d. 8.11 x 10^(-10)

Feedback

The correct answer is: 15.5 x 10^(-10)

The sequence components of phase a current are: Zero sequence current = 0.47 + j1.49, Positive

sequence current = 18.4 cis (-31.6 degrees), Negative sequence current = 3.23 cis (168.2 degrees).

Determine the phase b current.

Select one:

a. 18 cis 215 degrees

b. 19 cis 220 degrees

c. 20 cis 225 degrees

d. 15 cis 240 degrees

Feedback

The correct answer is: 18 cis 215 degrees

Two similar charges of 250 statC are situated on small spheres 15 cm apart. What is the potential at point

midway between the spheres?

Select one:

a. 25 statV

b. 16.7 statV

c. 66.7 statV

d. 33.3 statV

Feedback

The correct answer is: 16.7 statV

If a body is considered as a conducting sphere of 0.5 m radius, its capacitance to infinity is

Select one:

a. 55 nF

b. 55 uF

c. 55 pF

d. 55 F

Feedback


A circuit consisting of three resistors rated: 10 ohms, 15 ohms and 20 ohms are connected in delta. What

would be the resistance of the equivalent wye connected load?

Select one:

a. 3.0, 4.0 & 5.0 ohms

b. 3.33, 4.44 & 6.66 ohms

c. 0.30, 0.23 & 0.15 ohm

d. 5.77, 8.66 & 11.55 ohms

Feedback

The correct answer is: 3.33, 4.44 & 6.66 ohms

Two wattmeters are connected are for the two wattmeter method with current coils in lines A and B of a

208 V, ABC circuit that has a balanced delta load. If the meter readings arte 6 kW and -3 kW respectively,

find the load impedance per phase.

Select one:

a. 8.18 cis (79.1 deg) ohms/phase

b. 18.8 cis (-35.2 deg) ohms/phase

c. 32.2 cis (36.2 deg) ohms/phase

d. 22.3 cis (-36.2 deg) ohms/phase

Feedback

The correct answer is: 8.18 cis (79.1 deg) ohms/phase

A moving coil instrument having meter resistance of 5 ohms is to be used as a voltmeter 0 - 100 volts. If

the full-scale deflection current is 10 mA, the required series resistance is

Select one:

a. 1000 ohms

b. 9995 ohms

c. none of these

d. 20 ohms

Feedback


Solenoid 25 cm long is wound with 200 turns, what is the value of the field strength inside the solenoid,


Select one:

a. 1200 AT/m

b. 1000 AT/m

c. 1600 AT/m

d. 1400 AT/m

Feedback


A galvanometer with a 20-ohm coil resistance has a full-scale deflection current of 10 mA. If a 0.02 ohm is

placed across the meter to increase its capacity, what is the approximate new full scale current of the

meter?

Select one:

a. 10.01 A

b. 10.11 A

c. 11.01 A

d. 10.10 A

Feedback


Two incandescent lamps of 100 W, 200 V are in parallel across 200 V supply. The total resistance will be

____.

Select one:

a. 400 ohms

b. 800 ohms

c. 200 ohms

d. 600 ohms

Feedback


What is the force between a point charge 2 x 10^-5 coulomb and another 3 x 10^-6 coulomb when they

are 10 cm apart in vacuum?

Select one:

a. 45.5 kg

b. 53.95 kg

c. 5.395 x 10^-3 kg

d. 5.5 kg

Feedback

The correct answer is: 53.95 kg

The r.m.s. value of the complex voltage given by v = 16*(2^1/2) sin wt + 12*(2^1/2) sin 3wt is

Select one:

a. 192

b. 28*(2^1/2)

c. 20

d. 20*(2^1/2)

Feedback


The magnetic flux of 2000 lines is how many in maxwells?

Select one:

a. 8000

b. 1000

c. 2000

d. 4000

Feedback


What is 10^12 ergs/sec in kW?

Select one:

a. 100 kW

b. 10,000 kW

c. 1,000 kW

d. 10 kW

Feedback

The correct answer is: 100 kW

Question 1

Correct



Question text

To test the accuracy of a kilowatt-hour meter an

electrician used a wattmeter. He found out that the

meter makes 5 revolutions in 18 seconds. The meter

constant is 3.2. What is the percentage error if the

wattmeter reading is 3368?

Select one:

a. 8% slower

b. 5% faster

c. 5% slower Correct

d. 8% faster

Feedback


Question 2

Incorrect



Question text

A magnetomotive force is supplied by a current of

one ampere through 100 turns. The magnetic circuit

consists of a steel core of 1000 permeability, 10 cm

long and 4 sq. cm area and an air gap one cm long.

What is the field intensity at the air gap?

Select one:

a. 100.53 oersted

b. 12.25 oersted

c. 497.66 oersted Incorrect

d. 124.4 oersted

Feedback

The correct answer is: 124.4 oersted

Question 3

Correct



Question text

A parallel plate capacitor is made of 350 plates,

separated by paraffin paper 0.0010 cm thick (k =

2.5). The effective size of plate is 15 by 30 cm. What

is the capacitance of this capacitor?

Select one:

a. 140 uF

b. 70 uF

c. 15 uF

d. 35 uF Correct

Feedback


Question 4

Incorrect



Question text

To double the current range of a 50-micro-amp, 2

kilo-ohm moving coil meter movement, the shunt

resistance should be

Select one:

a. 2 kilo-ohms

b. 1 kilo-ohm

c. 18 kilo-ohms Incorrect

d. 50 kilo-ohms

Feedback


Question 5

Correct



Question text

If an alternating voltage has a magnitude of 10 V at

30 degrees, what is its maximum voltage?

Select one:

a. 30 V

b. 40 V

c. 50 V

d. 20 V Correct

Feedback


Question 6

Correct



Question text

A wire carries a current i = 3 cos 314t amperes.

What is the average current over 6 seconds?

Select one:

a. 0 A Correct

b. 3.0 A

c. 0.532 A

d. 1.5 A

Feedback


Question 7

Correct



Question text

What is the flux density having a flux of 12,000

maxwells through a perpendicular area of 6 cm

squared?

Select one:

a. 2,000 gauss Correct

b. 200 gauss

c. 72,000 gauss

d. 72 gauss

Feedback

The correct answer is: 2,000 gauss

Question 8

Correct



Question text

The result of capacitance C1 = 6 microfarads and

C2 connected in series is 3 microfarads. Capacitor

C2, in microfarads is

Select one:

a. 3

b. 6 Correct

c. 8

d. 4

Feedback


Question 9

Correct



Question text

MERALCO used two wattmeters to measure the

balanced 3-phase dynatron elevator motor drive.

The coils of the wattmeters are connected to the

current transformers, which are lines 1 and 2

respectively. The potential coils are connected to

potential transformers, which are across lines 2 and

3 and lines 3 and 1, respectively. The line potentials

are 230 V and the line currents are each 150 A. The

wattmeters each indicate 19.6 kW. Assume load is

wye connected. What is the total power supplied?

Select one:

a. 45.461 kW

b. 49.175 kW Correct

c. 47.350 kW

d. 48.236 kW

Feedback


Question 10

Not answered

Marked out of 1.00


Question text

The torque of a spring controlled ammeter varies as

the square of the current thru it. If the current of 5

amperes produces deflection of 90 degrees, the

deflection in degrees for a current of 3 amperes is

____.

Select one:

a. 18

b. 32.4

c. 30

d. 54

Feedback


Question 11

Incorrect



Question text

A galvanometer has a resistance of 300 ohms. What

is the ohmic resistance to make it read one is to ten?

Select one:

a. 33.33

b. 30 Incorrect

c. 10

d. 100

Feedback


Question 12

Correct



Question text

Solenoid 25 cm long is wound with 200 turns, what

is the value of the field strength inside the solenoid,


Select one:

a. 1000 AT/m

b. 1600 AT/m Correct

c. 1400 AT/m

d. 1200 AT/m

Feedback


Question 13

Correct



Question text

If three 100-pf capacitors are connected in series,

then the total capacitance is

Select one:

a. 300 pF

b. 50 pF

c. 33.3 pF Correct

d. 100 pF

Feedback

The correct answer is: 33.3 pF

Question 14

Correct



Question text

A sinusoidal voltage wave has an RMS value of

70.71 V and a frequency of 60 Hz. Determine the

value of the voltage 0.0014 second after the wave

crosses the wt axis.

Select one:

a. 70.71 V

b. 100 V

c. 50 V Correct

d. 141.42 V

Feedback


Question 15

Incorrect



Question text

A 12 micro-farad capacitor charged at 500 Volts and

a 6 micro-farad capacitor charged at 250 Volts are

connected in parallel. What is the potential

difference in the combination?

Select one:

a. 750 Volts Incorrect

b. 417 Volts

c. 500 Volts

d. 450 Volts

Feedback


Question 16

Correct



Question text

How long can a battery last with capacity of 50

ampere-hour running equipment of 5 amperes?

Select one:

a. 10 hours Correct

b. 250 hours

c. 100 hours

d. 25 hours

Feedback

The correct answer is: 10 hours

Question 17

Correct



Question text

Two coils of inductances 4 H and 6 H are connected

in parallel such that their mutual inductance is 3 H

assists the self-inductance. The total inductance of

the combination is ____.

Select one:

a. 8.25 H

b. 2.06 H

c. 3.75 H Correct

d. 0.94 H

Feedback


Question 18

Incorrect



Question text

Two parallel wires 10 cm apart carry current in the

opposite direction of 8 A. What is the magnetic field

halfway between them?

Select one:

a. 32 x 10^-6 T

b. 16 x 10^-6 T Incorrect

c. 8 x 10^-6 T

d. 64 x 10^-6 T

Feedback

The correct answer is: 64 x 10^-6 T

Question 19

Not answered

Marked out of 1.00


Question text

Two similar poles, each of 1 Wb, placed 1 m apart in

air will experience a repulsive force of

Select one:

a. 796 kN

b. 63 x 10^-3 N

c. 63000 N

d. 8 x 10^12 N

Feedback

The correct answer is: 63000 N

Question 20

Correct



Question text

If a body is considered as a conducting sphere of

0.5 m radius, its capacitance to infinity is

Select one:

a. 55 nF

b. 55 uF

c. 55 pF Correct

d. 55 F

Feedback


Question 21

Correct



Question text

A certain electric welder has a basic circuit

equivalent to a series RL with R = 0.1 ohm and L = 1

mH. It is connected to an AC source e through a

switch s operated by an automatic timer, which

closes the circuit at any desired point on the 60

cycle, sinusoidal wave e. Calculate the magnitude of

the transient current resulting when s closes as e is

passing through its peak value of 100 volts.

Select one:

a. 256.41 A

b. 76.32 A

c. 65.74 A Correct

d. 80.54 A

Feedback


Question 22

Not answered

Marked out of 1.00


Question text

A 1% d Arsonval meter movement has coil and

swamping resistance adding to 200 ohms. The full-

scale voltage is 50 mV. Determine the shunt

resistance required producing 1 A full scale current

meter.

Select one:

a. 48.74 milli-ohms

b. 49.22 milli-ohms

c. 50.01 milli-ohms

d. 52.02 milli-ohms

Feedback

The correct answer is: 50.01 milli-ohms

Question 23

Correct



Question text

In symmetrical components, what is the vector sum

of 1 + a + a^2?

Select one:

a. infinity

b. -1

c. 0 Correct

d. 1

Feedback


Question 24

Not answered

Marked out of 1.00


Question text

A 35 unit south pole is placed 1 inch to a 20 unit

south pole. Determine the force between the poles.

Select one:

a. 129.5, repulsion

b. 129.5, attraction

c. 108.5, attraction

d. 108.5, repulsion

Feedback

The correct answer is: 108.5, repulsion

Question 25

Incorrect



Question text

Twenty-four (24) dry cells are arranged in rows of six

(6) in series and the four (4) rows in parallel. The

emf of each cell is 1.40 Volt, and internal resistance

of each is 0.08 ohm. Determine the current to an

external resistor of 3.2 ohms.

Select one:

a. 2.53 A Incorrect

b. 5.23 A

c. 5.32 A

d. 2.35 A

Feedback


Question 26

Correct



Question text

In an RL circuit, Kirchhoff law gives the following

relation: E = Ldi/dt + Ri where: E = supply voltage

(200 volts), R = resistance (20 ohms), L =

inductance (1 Henry), t = time in seconds, i = current

in amperes. If i = 0 when t = 0, find i when t = 0.02

second.

Select one:

a. 3.3 A Correct

b. 3.2 A

c. 3.1 A

d. 3.0 A

Feedback


Question 27

Correct



Question text

An electric heater carries 12 A at 110 V, is

submerged in 22.5 lbs of water for 30 minutes. What

will be the final temperature of the water if its initial

temperature is 35 degrees F?

Select one:

a. 133.56 degrees F

b. 135.43 degrees F Correct

c. 125.42 degrees F

d. 128.33 degrees F

Feedback

The correct answer is: 135.43 degrees F

Question 28

Correct



Question text

A 6.0 H coil whose resistance is 12 ohms is

connected in series with a 24 ohms resistor and to a

144 V battery and a switch. The switch is closed at t

= 0. Determine the energy stored in the magnetic

field at steady state.

Select one:

a. 46 J

b. 50 J

c. 52 J

d. 48 J Correct

Feedback

The correct answer is: 48 J

Question 29

Not answered

Marked out of 1.00


Question text

A coil has 2500 turns and a current of 10 A flowing

in it produces an effective flux of 0.05 Weber. If the

resistance is 12 ohm, what is the time constant of

the coil

Select one:

a. 1.12 sec

b. 2.25 sec

c. 1.0 sec

d. 0.75 sec

Feedback

The correct answer is: 1.12 sec

Question 30

Correct



Question text

What is the size in square millimeter (mm^2) is the

cable of 250 MCM size?

Select one:

a. 126.675 mm^2 Correct

b. 132.348 mm^2

c. 118.656 mm^2

d. 112.565 mm^2

Feedback

The correct answer is: 126.675 mm^2

Question 31

Correct



Question text

An analog ohmmeter reads 18 on R X 10 k range.

What is the value of the measured resistance?

Select one:

a. 18 ohms

b. 18 kilo-ohms

c. 180 ohms

d. 180 kilo-ohms Correct

Feedback


Question 32

Correct



Question text

An inductor draws 5 A of current at 110 volts, 60 Hz.

Determine the inductance.

Select one:

a. 56.38 mH

b. 58.36 mH Correct

c. 38.56 mH

d. 53.68 mH

Feedback


Question 33

Correct



Question text

If a force of 4.8 x 10^(-2) N is required to move a 40

uC charge in an electric field between two points 20

cm apart. What is the potential difference between

two points?

Select one:

a. 240 Volts Correct

b. 360 Volts

c. 120 Volts

d. 160 Volts

Feedback


Question 34

Correct



Question text

Three resistors 10, 15 and 30 ohmic values are

connected in wye-configuration to a balanced 208

volt three-phase supply. Calculate the total power of

the system.

Select one:

a. 2880 W

b. 3280 W

c. 3080 W

d. 2644 W Correct

Feedback

The correct answer is: 2644 W

Question 35

Correct



Question text

A DC voltage of 80 volts is applied to a circuit

containing a resistance of 80 ohms in series with an

inductance of 20 Henry. Calculate the growth of

current at the instant of completing the circuit.

Select one:

a. 2 A/s

b. 1/4 A/s

c. 1/2 A/s

d. 4 A/s Correct

Feedback

The correct answer is: 4 A/s

Question 36

Correct



Question text

Twelve similar wires each of resistance 2 ohms are

connected so as to form a cube. Find the resistance

between the two corners of the same edge.

Select one:

a. 1.167 ohms Correct

b. 1.133 ohms

c. 1.102 ohms

d. 1.125 ohms

Feedback


Question 37

Correct



Question text

Determine the rms value of a semi-circular current

wave which has a maximum value of A.

Select one:

a. 0.23 A

b. 0.816A Correct

c. 0.707A

d. 0.866A

Feedback

The correct answer is: 0.816A

Question 38

Correct



Question text

A current of 10 amperes at a power factor of 0.8

lagging is taken from 250 V a.c. supply. The reactive

power of the system is

Select one:

a. 1500 VAR Correct

b. 2000 VA

c. 1500 watts

d. 2000 watts

Feedback

The correct answer is: 1500 VAR

Question 39

Not answered

Marked out of 1.00


Question text

What is the coefficient of coupling of two coils whose

mutual inductance is 1 H and whose self-

inductances are 1.2 and 2 H?

Select one:

a. 0.645

b. 0.912

c. 2.400

d. 1.549

Feedback


Question 40

Not answered

Marked out of 1.00


Question text

A magnetic coil produces 100,000 Maxwell with

2,000 turns and with a current of 2 A. The voltage is

cut-off and the flux collapses in 0.01 sec. What is the

average voltage that will appear across the coil?

Select one:

a. 20 kV

b. 2,000 kV

c. 2 kV

d. 200 V

Feedback


Question 41

Correct



Question text

A current transformer has a single turn primary and

a 200 turn secondary and is used to measure a.c.

current with the help of a standard 5-A a.c. ammeter.

These arrangements can measure a line current of

up to ____ ampere,

Select one:

a. 40

b. 200

c. 1000 Correct

d. 5000

Feedback


Question 42

Incorrect



Question text

The stator of a 440 V, 50 HP shunt motor is tested at

75 degrees C for its insulation resistance between

terminals connected together and the ground frame.

When a 50,000 ohm voltmeter is connected in series

with a 600 V DC source, the meter indicates 125 V.

Calculate the insulation resistance.

Select one:

a. 190 kilo-ohms

b. 170 kilo-ohms

c. 200 kilo-ohms

d. 180 kilo-ohms Incorrect

Feedback


Question 43

Correct



Question text

An ammeter has a range of 0 - 10 amps. What is

shunt resistance to be connected if the range is

increased to 100 amps? The internal resistance of

the ammeter is 0.10 ohms.

Select one:

a. 2.111 ohms

b. 0.0111 ohms Correct

c. 0.111 ohms

d. 1.111 ohms

Feedback


Question 44

Correct



Question text

A circuit draws 25 A when connected across a

source of frequency f1. Determine the current drawn

by the same circuit at resonance if f1 is half the

resonant frequency.

Select one:

a. 12.5 A

b. 50 A

c. 35.35 A Correct

d. 17.68 A

Feedback


Question 45

Correct



Question text

A generator has a field winding with an inductance L

= 10 Henry and a resistance Rf = 0.1 ohm. To break

the initial field current of 1000 amperes, the field

breaker inserts a field discharge resistance Rd

across the field terminals before the main contacts

open. As a result, the field current decays to zero

according to the differential equation. L*di/dt + i*R =

0, Where: R = Rf + Rd preventing a sudden

decrease of i to zero, and a resulting high inductive

voltage due to L. Solve the differential equation and

determine the value of Rd that would limit the initial

voltage across it to 1,000 volts

Select one:

a. 0.95 ohm

b. 0.90 ohm Correct

c. 0.85 ohm

d. 0.80 ohm

Feedback

The correct answer is: 0.90 ohm

Question 46

Incorrect



Question text

A capacitor is charged with 0.23 watt-second of

energy at a voltage of 48 volts. What is its

capacitance?

Select one:

a. 220 uF

b. 180 uF

c. 240 uF Incorrect

d. 200 uF

Feedback


Question 47

Correct



Question text

A magnet which generates 800 Maxwell of flux, is

inserted through a coil of 1000 turns. It is then

withdrawn within 0.15 sec. What is the voltage that

appears across the coil?

Select one:

a. 0.22 V

b. 533 V

c. 0.0533 V Correct

d. 53.3 V

Feedback

The correct answer is: 0.0533 V

Question 48

Incorrect



Question text

Find the capacitance of a two plate capacitor of plate

area 12 sq. inch dielectric constant of 6 and

dielectric thickness of 0.01 inch.

Select one:

a. 1.6 nF

b. 1.5 nF

c. 1.2 nF Incorrect

d. 1.3 nF

Feedback

The correct answer is: 1.6 nF

Question 49

Incorrect



Question text

Four capacitors A, B, C and D are connected across

a 15-V DC source. The charges accumulated in A, B

and C are equal to 2000, 750 and 1500 uC,

respectively. If the total capacitance of the

combination is known to be 35 uF, how much charge

is accumulated in capacitor D?

Select one:

a. 1000 uC

b. 1400 uC

c. 1200 uC Incorrect

d. 1500 uC

Feedback


Question 50

Incorrect



Question text

A power plant customer draws power at 220 volts

from transformers on a pole. Current transformers

with a ratio of 200/5 are used to meter the electrical

usage. What is the multiplier of the kW-hr and

demand meters?

Select one:

a. 40

b. 100

c. 200 Incorrect

d. 80

Feedback


A parallel plate capacitor with air between its plates is charged until the

potential difference V appears across it. Another capacitor having hard

rubber (dielectric constant = 3) between its plates but otherwise identical,

is also charged to the same potential difference. If the energy of the first

capacitor is W, that of the second is

Select one:

a. 3W

b. W/3

c. W

d. 9W

Feedback

The correct answer is: 3W

A process equipment contains 100 gallons of water at 25 degrees C. It is

required to bring it to boiling in 10 minutes. The heat loss is estimated to

be 5%. What is the kW rating of the heater?

Select one:

a. 125 kW

b. 252 kW

c. 50.5 kW

d. 207 kW

Feedback

The correct answer is: 207 kW

A capacitor branch having a ratio of XC to R of 5 is paralleled with

impedance consisting of a 4 ohms resistance and a 3 ohms inductive

reactance. The power factor of the resulting circuit is 0.8 leading. Find

the size of the capacitor in uF if the frequency is 60 Hz.

Select one:

a. 879.9 uF

b. 1078.9 uF

c. 778.9 uF

d. 978.9 uF

Feedback


A 230 V single-phase meter has a constant load current of 4 amp

passing through the meter for five hours at unity p.f. If the meter disk

makes 1,104 revolutions during this period, solve for the meter constant

in rev/kWh.

Select one:

a. 120

b. 480

c. 360

d. 240

Feedback


Two (2) 115-V incandescent lamps A and B are connected in series

across a 230-V source. If lamp A is rated 75 watts and lamp B is rated

50 watts, determine the current drawn by the series connection.

Select one:

a. 0.57 A

b. 0.48 A

c. 0.64 A

d. 0.52 A

Feedback


A 6 H coil whose resistance is 12 ohms is connected in series with a 24

ohms resistor and to a 144 V battery and a switch. The switch is closed

at t = 0. Determine the current at t = 0.1 second.

Select one:

a. 1.624 A

b. 1.805 A

c. 1.750 A

d. 1.538 A

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Installed in one of the customer CEPALCO are two single phase

transformers each rated 75 kVA are connected V or open delta to serve

a 3-phase load of 120 kW at 0.8 e.m.f. lagging. To prevent the

overloading of the transformers, determine the size of the capacitor in

kVAR.

Select one:

a. 41

b. 40

c. 39

d. 42

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Two metallic plates separated by 1 cm are connected across a 12 V

battery. A certain material is inserted completely filling the space

between the plates and the charge on each plate observed to double.

What is the dielectric constant of the plastic material?

Select one:

a. 6

b. 0.5

c. 2

d. 4

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Two coils of inductance L1 = 1.16 mH, L2 = 2 mH are connected in

series. Find the total energy stored when the steady current is 2 Amp.

Select one:

a. 17.5 mJ

b. 63,2 mJ

c. 6.32 mJ

d. 1.75 mJ

Feedback

The correct answer is: 17.5 mJ

A sinusoidal voltage wave has an RMS value of 70.71 V and a frequency

of 60 Hz. Determine the value of the voltage 0.0014 second after the

wave crosses the wt axis.

Select one:

a. 70.71 V

b. 141.42 V

c. 100 V

d. 50 V

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A milliameter with full-scale deflection of 1 mA and a resistance of 25

ohms was used to measure an unknown current by shunting the meter

with a 1-ohm resistor. The meter then reads half-scale. What is the

unknown value?

Select one:

a. 130 mA

b. 125 mA

c. 12.5 mA

d. 13 mA

Feedback

The correct answer is: 13 mA

A coil has an impedance of 75.4 ohm when connected a across a source

of 60 Hz. The same coil yields an impedance of 54.8 ohms when

connected across a source having a different frequency of 30 Hz. What

is the inductance of the coil?

Select one:

a. 341.7 mH

b. 245.7 mH

c. 158.6 mH

d. 512.8 mH

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A parallel circuit with one branch of R = 5 ohms and a single unknown

element in the other branch has the following applied voltage and total

current e = 10 cos (50t + 60 deg) V and i = 5.38 cos (50t - 8.23 deg) A.

The unknown element is ____.

Select one:

a. L = 0.04 H

b. C = 5 uF

c. L = 0.02 H

d. C = 10 uF

Feedback

The correct answer is: L = 0.04 H

A permanent magnet loudspeaker is equipped with a 10 ohm voice coil

wound on a tube 1 inch in diameter. The flux density in the air gap is

10,000 lines per square inch. If the impedance of the voice coil is a pure

resistance, what will be the maximum thrust delivered to the core if the

impressed signal is 20 dB above 0.005 watt?

Select one:

a. 0.0532 N

b. 0.0336 N

c. 0.0116 N

d. 0.0276 N

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Four capacitors A, B, C and D are connected across a 15-V DC source.

The charges accumulated in A, B and C are equal to 2000, 750 and

1500 uC, respectively. If the total capacitance of the combination is

known to be 35 uF, how much charge is accumulated in capacitor D?

Select one:

a. 1200 uC

b. 1400 uC

c. 1000 uC

d. 1500 uC

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A 200 volt DC supply is suddenly switched to a relay coil which has a

time constant of 3 ms. If the current in the coil reaches 0.20 ampere after

3 ms determine the steady state value of the current.

Select one:

a. 0.316 A

b. 0.361 A

c. 0.163 A

d. 0.631 A

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A single-phase three wire, 60 Hz, 220 V, watthour meter has a disc

constant of 1.2. Determine the energy recorder by the meter after 18,000

revolutions of the disc.

Select one:

a. 21.6 kW-hr

b. 20.5 kW-hr

c. 25.4 kW-hr

d. 27.6 kW-hr

Feedback

The correct answer is: 21.6 kW-hr

A 3-phase, 3-wire load draws the following line currents: Ia = 60 cis (330

deg) A, Ib = 78.4 cis (214 deg) A, Ic = 75 cis (80 deg) A. If the voltages

impressed on the load are balanced 3-phase, having a magnitude of

4140 volts line to line, solve for the total power in kW.

Select one:

a. 506.85

b. 536.54

c. 556.16

d. 520.18

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An iron core 0.4 m long and 5 square cm in cross-section is wound with

300 turns. When a current of 0.5 A flows in the coil, how much is the

inductance of the coil. Assume the core has a permeability of 2500.

Select one:

a. 0.35 H

b. 0.42 H

c. 0.31 H

d. 0.26 H

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A lead-sheath cable for underground service has a copper conductor

(diameter = 0.350 inch) surrounded by 0.20 inch wall of rubber

insulation. Assuming the dielectric constant of 4.3 for rubber, calculate

the capacitance of the cable per mile length.

Select one:

a. 0.504 uF/mile

b. 0.76 uF/mile

c. 1.01 uF/mile

d. 0.252 uF/mile

Feedback

The correct answer is: 0.504 uF/mile

Two similar charges of 250 statC are situated on small spheres 15 cm

apart. What is the potential at point midway between the spheres?

Select one:

a. 66.7 statV

b. 16.7 statV

c. 33.3 statV

d. 25 statV

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The correct answer is: 16.7 statV

Two point charges Q1 = 50 microcoulombs and Q2 = 10 microcoulombs

are located at (-1, 1, 3) and (3, 1, 0) meters respectively. Find the

magnitude of the force on Q1.

Select one:

a. 4.9 N

b. 0.018 N

c. 74 N

d. 124.5 N

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A 12 V source with 0.05 ohm resistance is connected in series with

another 12 volt with 0.075 ohm resistance with a load of 2 ohms.

Calculate the power dissipated in the load.

Select one:

a. 255 watts

b. 127 watts

c. 105 watts

d. 365 watts

Feedback

The correct answer is: 255 watts

A parallel plate capacitor has the following values: k = 81, d = 0.025

inches; A = 6 square inches. What is the capacitance of the capacitor?

Select one:

a. 437.2 picofarad

b. 4372 picofarad

c. 43.72 picofarad

d. 4.372 picofarad

Feedback

The correct answer is: 4372 picofarad

A series loop contains the following circuit elements in order: an 8-Volt

source, 2 k ohms resistor. A 3 k ohms resistor, a 16-Volt source and a 7

k ohms resistor. What is the voltage across the 2 k ohms resistor?

Source Voltage are additive.

Select one:

a. 14 volts

b. 6 volts

c. 4 Volts

d. 8 volts

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A solenoid has an inductance of 1.58 mH. How many turns of wire does

it have if the solenoid is 25 cm long and its radius is 2.5 cm?

Select one:

a. 350 turns

b. 400 turns

c. 160,000 turns

d. 600 turns

Feedback

The correct answer is: 400 turns

A 6 H coil whose resistance is 12 ohms is connected in series with a 24

ohms resistor and to a 144 V battery and a switch. The switch is closed

at t = 0. Determine the time constant and the steady state current of the

circuit.

Select one:

a. 0.45 sec, 4 A

b. 0.66 sec, 3 A

c. 0.36 sec, 12 A

d. 0.50 sec, 6 A

Feedback

The correct answer is: 0.50 sec, 6 A

A 4 kW electric heater has a resistance of 1 kilo-ohm and an inductance

of 5 mH. If the current that flows through this coil produces a 2 mWb flux.

Calculate the reluctance of the coil.

Select one:

a. 5000

b. 0.0025

c. 3000

d. 1250

Feedback


A wire 12 cm long and carrying a current of 30 A is placed in between

the pole face of a magnet whose magnetic flux density is 0.9 Tesla. If the

wire is inclined at an angle of 60 degrees from the plane of the magnetic

field, what is the force exerted on the wire?

Select one:

a. 3.1 N

b. 2.2 N

c. 2.5 N

d. 2.8 N

Feedback


If a balanced delta load has an impedance of (6 + j9) ohms per phase,

then impedance of each phase of equivalent star load is

Select one:

a. (3 + j4.5) ohms

b. (6 + j9) ohms

c. (2 + j3) ohms

d. (12 + j18) ohms

Feedback

The correct answer is: (2 + j3) ohms

A battery can deliver 10 joules of energy to move 5 coulombs of charge.

What is the potential difference between the terminals of the battery?

Select one:

a. 2 V

b. 5 V

c. 0.5 V

d. 50 V

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Four identical capacitors of 2 uF each are charged to 50 V, 100 V, 200 V

and 250 V, respectively. They are then connected in parallel across an

uncharged 4 uF capacitor. What is the voltage across the 4 uF

capacitor?

Select one:

a. 50 V

b. 300 V

c. 120 V

d. 100 V

Feedback


A capacitor with air between its plates has a capacitance of 3 uF. What

is the capacitance when wax of dielectric constant 2.8 is between the

plates?

Select one:

a. 8.40 uF

b. 23.52 uF

c. 1.07 uF

d. 0.38 uF

Feedback


To double the current range of a 50-micro-amp, 2 kilo-ohm moving coil

meter movement, the shunt resistance should be

Select one:

a. 2 kilo-ohms

b. 50 kilo-ohms

c. 1 kilo-ohm

d. 18 kilo-ohms

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A voltmeter using a 20 micro-amp meter movement has an ohm/V rating

of

Select one:

a. 1 kilo-ohm/V

b. 10 mega-ohms/V

c. 20 kilo-ohms/V

d. 50 kilo-ohms/V

Feedback

The correct answer is: 50 kilo-ohms/V

A power plant customer draws power at 220 volts from transformers on a

pole. Current transformers with a ratio of 200/5 are used to meter the

electrical usage. What is the multiplier of the kW-hr and demand meters?

Select one:

a. 200

b. 80

c. 100

d. 40

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A condenser of 1 microfarad capacitance is charged to 100 volts and

then disconnected from the power supply. A second but uncharged

capacitor of 3 microfarad is connected across the first capacitor. The

voltage across the parallel combination is

Select one:

a. 45 volts

b. 110 volts

c. 25 volts

d. 66 2/3 volts

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The correct answer is: 25 volts

A metal transport plane has a wing spread of 88 ft. What difference of

potential exists between the extremities of the wings, when the plane

moves horizontally with the speed of 150 miles per hour? The value of

the vertical-component of the magnetic field of the earth is 0.65 Gauss at

the plane.

Select one:

a. 1.2 Volt

b. 0.12 volt

c. 0.24 Volt

d. 12 Volt

Feedback

The correct answer is: 12 Volt

Calculate the absolute permittivity of the material with relative permittivity

of 10.

Select one:

a. 8.854 x 10^-11 F/m

b. 8.884 x 10^-12 F/m

c. 8.854 x 10^-13 F/m

d. 8.841 x 10^-13 F/m

Feedback

The correct answer is: 8.854 x 10^-11 F/m

If an oscilloscope with a vertical deflection of 0.1 volt rms per centimeter

(cm), is used in conjunction with a 10 ohm shunt resistor to measure a

25 milli-amp current, compute the vertical deflection?

Select one:

a. 0.025 cm

b. 2.5 cm

c. 25 cm

d. 0.25 cm

Feedback

The correct answer is: 2.5 cm

A tank circuit is supplied by a current source whose source resistance is

56 kilo-ohms. The tank circuit is composed of a 56 nF capacitor in

parallel with a coil of inductance 35 mH and resistance 80 ohms.

Determine the resonant frequency.

Select one:

a. 4.6 kHz

b. 6.2 kHz

c. 3.6 kHz

d. 3 kHz

Feedback

The correct answer is: 3.6 kHz

Twelve resistances of 1 ohm each are arranged along the edge of a

cube with junctions at corners. What resistance will be measured

between terminals of symmetrically opposite corners of the cube?

Select one:

a. 5/9 ohm

b. 5/6 ohm

c. 6/5 ohm

d. 6/11 ohm

Feedback

The correct answer is: 6/5 ohm

A magnetic ring (relative permittivity = 800) has a mean radius of 10 cm

and a cross-sectional area of 5 cm^2. An air gap measuring 1.5 mm is

cut in the ring. Determine the required mmf in order to produce a flux of

0.25 mWb in the air gap.

Select one:

a. 909

b. 920

c. 890

d. 972

Feedback


The torque of a spring controlled ammeter varies as the square of the

current thru it. If the current of 5 amperes produces deflection of 90

degrees, the deflection in degrees for a current of 3 amperes is ____.

Select one:

a. 30

b. 32.4

c. 54

d. 18

Feedback


A current transformer has a single turn primary and a 200 turn

secondary and is used to measure a.c. current with the help of a

standard 5-A a.c. ammeter. These arrangements can measure a line

current of up to ____ ampere,

Select one:

a. 40

b. 1000

c. 200

d. 5000

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Three resistors of 10, 15 and 20 ohms each are connected in parallel.

What is the total conductance?

Select one:

a. 0.562 siemens

b. 3.41 siemens

c. 4.52 siemens

d. 0.217 siemens

Feedback

The correct answer is: 0.217 siemens

If a magnetic material is located within a coil through which alternating

current (50 Hz frequency) flows, then ____ hysteresis loops will be

formed every second.

Select one:

a. 150

b. 100

c. 50

d. 25

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A voltmeter with an internal resistance of 5000 ohms is calibrated to read

10 volts at full-scale. How much series resistance is needed in order to

measure 150 volts at full scale?

Select one:

a. 78 kilo-ohms

b. 70 kilo-ohms

c. 75 kilo-ohms

d. 72 kilo-ohms

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A current is represented by its equation 10 sin (wt + 30 deg) and 5 sin

(3wt - 30 deg). The magnitudes of the components are instantaneous

values. What is the rms value of the current?

Select one:

a. 1.1 amperes

b. 7.9 amperes

c. 10.6 amperes

d. 13.22 amperes

Feedback

The correct answer is: 7.9 amperes

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