Elecrtical April

MET march’131. *Open-loop transfer function of a system having one zero with positive real values is

called nonminimum phase function

2. * AC circuits possess characteristics of resistance, inductance, and capacitance.The capacitive reactance of acircuit is expressed inA.ohmsB.mhosC.henrysD.farads

3. *Which of the listed precautions should be taken when cleaning the internals of a motor with compressed air?(multi Ans)A.Open the machine on both ends so as to allow the air and dust to escape.B.Be certain that the circuit breaker is opened and tagged on the feeder panel.C.Be certain that the air is clean and as dry as possible.D.Ensure that the fuse in the motor is removed.

4. *Which of the following is having Di-Electric Constant 80?A.AirB. waterC. Mica D. Castor oil

5. Which of the listed devices may be installed on a large turbo-electric alternatingcurrent propulsion generator?A. Temperature detector coils inserted in the stator slots for measuring stator temperature.B. A CO2 fire extinguishing system.C. Electric space heaters to prevent condensation of moisture.D. All of the above.

6. *Tightly knit metal braid wire can be used with a printed circuit board when A.Conductor flexibility is requiredB.De-soldering components in the circuitC.Electrically produced magnetic fluxes would caus in adjacent componentsD.Reactance in the circuit must be kept to a minimum

7. Which of the listed conditions is an advantage of a PN diode over a vacuum diode?A. Longer life.B. No warm up time.C. Less delicate.D. All of the above.

8. *Calculate the frequency of the motor, if the speed if 4800 Rpm and number of Poles is 2. ( up to 0 decimal places)

9. *When reading electrical motor controller diagrams, it helps to know that ____________.A.current paths in control circuit are drawn as heavy lines &power circuit as lighter linesB.current paths in power circuit are drawn as heavy lines & control circuit as lighter linesC.circuits of 500V or greater are drawn as heavy lines and below 500V as lighter linesD.circuits of 500V or greater are drawn as light lines and below 500V as heavy lines

10.Which of the following conditions will occur when solenoid coil burns out of a cargo winch with a electrical brake.A.The brake will be set by spring force.B.The motor will over speed and burns outC.The load suspended by the cargo boom will failD.Nothing will happen, the winch will continue to operate normally

11.If an intrinsic semiconductor is doped with a very small amount of boron then the extrinsic semiconductor set formed, the no. of electrons and holes willA.both Dec. B.increase and decreaseC.Both increaseD.Decrease and increase

12.For leading power factor circuits, which of the following can be used?A.Shunt Capacitors onlyB.Shunt Reactors onlyC.Either Shunt Capacitors or Shunt ReactorsD.Neither Shunt Capacitors Nor Shunt Reactors

13. The RMS value of a sine-wave current may also be expressed as the _____________.A. average valueB. maximum valueC. effective valueD. instantaneous value

14.*Alfa particles enter an electromagnetic field where the electric intensity is 300v/m and the magnetic induction is 0.200T what is the velocity of Alfa particles?

15.* With reference to a Data Logger for a refrigeration system, which of the following parameters should be monitored?(multi ans)A.Sea water temperature and pressure.B.Condensing temperatureC.Refrigerant leakageD.Evaporating temperature

16.Where a thermal-acting breaker is required to be used in an area of unusually high, low, or constantly fluctuating temperatures, an ambient compensating element must be used. This element consists of aA.Cylindrical spring on the contact arm.

B.Conical spring on the contact arm.C.Second bimetal element.D.Second electromagnet.

17.*when the current through the coil of an electromagnet is reversed, the direction of magnetic field also reversed (TRUE or FALSE)

18.The current in a semiconductor is produced by(multiple ans)A.ElectronsB.NeutronsC.ProtonsD.Holes

19.*Vgs and Id approximately zero....this is called cutoff voltage

20.*A certain appliance uses 700 W. If it is allowed to run continuously for 36 days, how many kilowatt-hours of energy does it consume(up to 1 deci)

21.When paralleling an AC generator with live bus bars, which of the following precautions are applicable?(multi ans)A.Generator frequency should be slightly lower than bus bar frequencyB.Generator frequency should be slightly higher than bus bar frequencyC.Generator voltage should be in phase with bus bar voltageD.Generator voltage should be out of phase with bus bar voltage

22.A delayed action fuse is most frequently used in which of the listed A.lighting cutoutB.motor cutoutC.electrical heaterD. padar circuit

23.*A poly-phase motor driving an engine room pump fails to start. When trying to identify the cause of failure, which of the following steps are applicable?(Multi Ans)A. Ensure that the isolator is open.B. Make sure that there is no restriction preventing movement of pump/motor.C. Check whether the overload relay has tripped.D. Check whether battery is fully charged

24.*Resistances of 20,15,25 ohm are connected in series across a 36 V line. Caluclate voltage drop across 25 ohm resistance?

25.Poly phase fails to start, precautions to take before checking(multi ans)A.Isolate motorB.Remove fuse

C.post caution signD.Ensure starter/motor terminals are live

26. 1.A certain appliance use 350W, if it is allowed to run continous for 24 days , how many kw of energy does it consume (fill in the blank)

27. Ans-28. 2.open loop <<>> function of a sys has zero with positive real

value is called NON MINIMUMphase function29. 3.If an intrinsic semiconductor is doped with a very small amount

of boron then the extrinsic semiconductor set formed ,the no. of electrons and holes willA.bothdecB.increase and decreaseC.Both increaseD.Decrease and increase

30. 4.when the current through the coil of an electromagnet is reversed, the direction of magnetic field also reversed (TRUE or FALSE)

31. 5.A poly phase motor driving an engine room pump fails to start, when trying to identify the cause of failure, which of the following steps are applicable.(multiple ans)A.visually examine the motor for open circuit faultB. visually examine the stator for open circuit faultC.Reverse the direction of current for its workingD.Perform the infinite resistance test

32. 6.with reference to the data logger for a refrigerate sys. Which of the parameters should be noted.A.sea water temp, pressureB.condenser tempC.Refrigerent leakageD.Evaporator temp

33. 7.When a thrmal acting breaker is required to be used in a area of usually high,low and constant fluctuating temp. as ambient compensation <<>> must be used.the element consists ofA.cylindrical spring on the constant areaB.Conical spring ………………………………….C.Secondary bimetal elementD………electro magnet

34. 8.the voltage induced across a certain coil is 150 mA. a 100 ?? resistor is connected to the coil terminal calculate induced current in Milli Ampere ??????ans-

35.

9.Which of the listed precautions should be taken when cleaning the internals of a motor with compressed air?A. Open the machine on both ends so as to allow the air and dust to escape.B. Be certain that the circuit breaker is opened and tagged on the feeder panel.C. Be certain that the air is clean and as dry as possible.D. Ensure that the fuse in the motor is removed.

10.When reading electrical motor controller diagrams, it helps to know that ____________.A.current paths in the control circuit are drawn as heavy lines and in the power circuit as lighter linesB.current paths in the power circuit are drawn as heavy lines and in control circuit as lighter lines

C.circuits subject to 500 volts or greater are drawn as heavy lines and below 500 volts as lighter linesD.circuits subject to 500 volts or greater are drawn as light lines and below 500 volts as heavy

36. 11.In a TransistorA.PNP and NPN are two basic typesB.Emitter,Collector and Base are the basic Elements.C.Collector separates Base and EmitterD.Emitter separates Base and Collector

37. 12.Tightly knit metal braid wire can be used with a printed circuit board when A.Conductor flexibility is requiredB.De-soldering components in the circuitC.Electrically produced magnetic fluxes would cause inaccuracies in adjacent componentsD.Reactance in the circuit must be kept to a minimum

13.When paralleling an AC generator with live bus bars, which of the following precautions are applicable?A.Generator frequency should be slightly lower than bus bar frequencyB.Generator frequency should be slightly higher than bus bar frequencyC.Generator voltage should be in phase with bus bar voltageD.Generator voltage should be out of phase with bus bar voltage

38. 14.For leading power factor circuits, which of the following can be used?A.Shunt Capacitors only

B.Shunt Reactors onlyC.Either Shunt Capacitors or Shunt Reactors

39. D.Neither Shunt Capacitors Nor Shunt Reactors40. 15.A molded-case breaker provides protection against short-

circuits by usinga/anA.Shading coil.B.Arc quencher.c.Electromagnet.D.Holding coil.

41. 16.Fuses placed in series with a thermal trip = - type circuit breaker are used forA.Time-delay protectionB.Short-circuit protectionC.Short duration surge protectionD.Sustained overload protection

42. 17.Open-loop transfer function of a system having one zero with positive real values is called (1)_NON MINIMUM_______

43. 18.What is the magnetomotive force in a 75-turn coil of wire when there are 4 A of current through it?

44. 19.If it takes 35 J of energy to move a charge of 6 C from one point to another, what is the voltage between the two points? Your answer should be correct to two decimals.

45. ANS 5.8346. 20.The basic measuring unit of inductance is the

A.coulombB.ohmC.faradD.henry

47.

1. Which of the following statements is true concerning a poly-phase synchronous propulsion motor?

A. The motor is started as an induction motor.

B. Resistance is gradually added to the rotor circuit.

C. The starting current is held below the rated current.

D. The field winding is energized for starting purposes only.

2. When reading electrical motor controller diagrams, it helps to know that ____________.

A. current paths in thecontrol circuit are drawnas heavy lines and in thepower circuit as lighterlines

B. current paths in thepower circuit are drawnas heavy lines and incontrol circuit as lighterlines

C. circuits subject to 500volts or greater aredrawn as heavy lines andbelow 500 volts as lighterlines

D. circuits subject to 500volts or greater aredrawn as light lines andbelow 500 volts as heavy

3. Alternating current circuits develop resistance, inductance andcapacitance. The inductance of a coil is expressed in_____________.

A. ohms B. mhos C. henrys D. farads

4. Large cable sizes are formed as individual conductors that maybe comprised of several smaller strands to __________.

A. obtain the flexibilityrequired for easyhandling

B. reduce the overall weightof the wire run

C. reduce the number ofsupports needed for ahorizontal overhead run

D. all of the above

5. Which of the following is having Di-Electric Constant 80?

A. Air B. water C. Mica D. Caster oil

6. Where a thermal-acting breaker is required to be used in an areaof unusually high, low, or constantly fluctuating temperatures, anambient compensating element must be used. This elementconsists of a ______________.

A. cylindrical spring on thecontact arm

B. conical spring on thecontact arm

C. second bimetal element

D. second electromagnet

7. Which of the following precautions should you take whensecuring propulsion generators and motors for an extendedperiod of time?

A. Disconnect the brushpigtails from theircontacts and circulateair through the units.

B. Disconnect the brushpigtails from theircontacts and dischargecarbon dioxide into theunits to keep them dry.

C. Lift the brushes fromcommutator collectorrings and use the built-inheater to preventmoisture accumulation.

D. Lift the brushes fromcommutator collectorrings and circulate cooldry air through the units.

8. The direction of magnetic flux changes when the direction of current is reversed.

True / False

9. In a Transistor

A. PNP and NPN are two basic typesB. Emitter,Collector and Base are the basic Elements.C. Collector separates Base and EmitterD. Emitter separates Base and Collector

9. 9. In a P-Type Semiconductor, the majority current Carriers are holes

10. In a Control Loop System, having Zero(0) Positive Real Values are called unstable 11. If a Motor is not rotating in the E/R, you will carry out the following Checks (multiple choice, 3 Questions of same type but Options were different )

A. Check for the isolation B. Rotate the Coupling with your handC. Check for the Circuit breakerD. Remove the fusesE Look for the Overload TripF. Visually Inspect the motor terminalsG. Visually Inspect the Starter TerminalsH. Carry out Infinite Resistance Test

14. Calculate the Velocity of the conductor (up to 0 decimal places), if terminal voltage is 2.2 V/m and the magnetic field strength is 0.2 T.

15. Calculate the frequency of the motor ( up to 0 decimal places),, if the speed if 4800 Rpm and number of Poles is 2.

16. If the resistance of any coil is 120 Ohm. Calculate the Resistance (up to 0 decimal places), when its Length is increased by 20% and its Diameter is increased by 50%.

17. What is the power in a Resistor in Milli Watts (up to 0 decimal places), having Resistance of 12 Ohm having a Potential Difference of 3 V.

18. Resistance of a wire is increased if the Length is increased and Area is reduced

19. Arrange the following in Increasing Order of their Doping Strength.

A. Collector, Emitter, BaseB. Base, Emitter, CollectorC. Emitter, Base, CollectorD. Emitter, Collector, Collector Base, Collector, Base

20. Which of the listed precautions should be taken when cleaningthe internals of a motor with compressed air?

A. Open the machine onboth ends so as to allowthe air and dust toescape.

B. Be certain that the circuitbreaker is opened andtagged on the feederpanel.

C. Be certain that the air isclean and as dry aspossible.

E. All of the above

A poly-phase motor driving an engine room pump fails to start. When trying to identify the cause of failure, which of the following steps are applicable?

A. Visually examine motor for open circuit faults.

B. Visually examine starter for open circuit faults.

C. Reverse the direction of electrical supply to check if it works.

D. Perform the infinite resistance test.

The type of the system whose transfer function is given by

G(S) =(s2+3)/(s5+s4+s3+3s2+2s) is:

Variable Answer Units Correct to

G NA 0 decimal

Tightly knit metal braid wire can be used with a printed circuit board when

A. Conductor flexibility is required

B. De-soldering components in the circuit

C.Electrically produced magnetic fluxes would cause inaccuracies in adjacent components

D. Reactance in the circuit must be kept to a minimum

Which of the following statements represents an application of a silicon controlled rectifier?

A. To provide DC power for a main propulsion motor.

B. For use as a voltage reference diode.

C. For sensing flame in an automated burner.

0

D. To eliminate power supply hum.

When paralleling an AC generator with live bus bars, which of the following precautions are applicable?

A. Generator frequency should be slightly lower than bus bar frequency

B. Generator frequency should be slightly higher than bus bar frequency

C. Generator voltage should be in phase with bus bar voltage

D. Generator voltage should be out of phase with bus bar voltage

A certain appliance uses 750 W. If it is allowed to run continuously for 15 days, how many kilowatt-hours of energy does it consume?


KwH KwH 0 decimal

With reference to a Data Logger for a refrigeration system, which of the following parameters should be monitored?

A. Room temperature.

B. Liquid Line temperature.

C. Recharge temperature.

D. Solenoid valve operation.

With reference to a Data Logger for a refrigeration system, which of the following parameters should be monitored?

A. Sea water temperature and pressure.

B. Condensing temperature

C. Refrigerant leakage

D. Evaporating temperature

Mark: 4 The induced voltage across a stationary conductor in a steady magnetic field is zero.

True

False For leading power factor circuits, which of the following can be used?

A. Shunt Capacitors only

270

B. Shunt Reactors only

C. Either Shunt Capacitors or Shunt Reactors

D. Neither Shunt Capacitors Nor Shunt Reactors

A molded-case breaker provides protection against short-circuits by usinga/an

A. Shading coil.

B. Arc quencher.

C. Electromagnet.

D. Holding coil.

Fuses placed in series with a thermal trip = - type circuit breaker are used for

A. Time-delay protection

B. Short-circuit protection

C. Short duration surge protection

D. Sustained overload protection

Which of the listed precautions should be taken when cleaning the internals of a motor with compressed air?

A. Open the machine on both ends so as to allow the air and dust to escape.

B. Be certain that the circuit breaker is opened and tagged on the feeder panel.

C. Be certain that the air is clean and as dry as possible.

D. Ensure that the fuse in the motor is removed.

A fuse that blows often should be replaced only with a fuse of

A. the recommended current and voltage rating

B. higher current and voltage rating

C. higher current and lower voltage rating

D. lower current and higher voltage rating

Open-loop transfer function of a system having one zero with positive real values is called (1)________ phase function.

Where a thermal-acting breaker is required to be used in an area of unusually high, low, or constantly fluctuating temperatures, an ambient compensating element must be used. This element consists of a

A. Cylindrical spring on the contact arm.

B. Conical spring on the contact arm.

C. Second bimetal element.

D. Second electromagnet.

Brushless generators are designed to operate without the use of

A. brushes

B. sliprings

C. commutators

D. all of the above

What is the magnetomotive force in a 75-turn coil of wire when there are 4 A of current through it?


MMF At 0 decimal

In what range of voltages is the transistor in the linear region of its operation?

A. 0 < VCE < 0.7 V

B. 0.7 < VCE < 1.4 V

C. 0.7 < VCE < VCE(max)

D. 0 < VCE < VCE(max)

The current in a semiconductor is produced by:

A. Electrons

B. Neutrons

C. Protons

D. Holes

AC circuits possess characteristics of resistance, inductance, and capacitance.The capacitive reactance of acircuit is expressed in

A. ohms

B. mhos

C. henrys

D. farads

The greatest detrimental effect on idle electrical equipment, such as cargo pump motors,is the

A. Loss of residualmagnetism.

B. Absorption of moisture in the insulation.

C. Insulation varnish flaking.

D. Dirt collecting on the windings.

If it takes 35 J of energy to move a charge of 6 C from one point to another, what is the voltage between the two points? Your answer should be correct to two decimals.


V volts 2 decimal

The basic measuring unit of inductance is the

A. coulomb

B. ohm

C. farad

D. henry

A semiconductor is damaged by a strong current, because of (1)________ (2)________ (3)________

1)

2)

3) Junctiom

-------GUYS LETS SOLVE THESE 25 ELECTRICAL NUMERICALS------

1. If resistance of any coil is 120 OHM. Calculate the resistance when its length is increased by 20% and its dia is increased by 50 % ( fill in the blank)

2. A certain appliances uses 750w. if it is allowed to run continuously for 15 days how many kilowatt of energy does it consume? (fill in the blank)

3. What is the mageto motive force in a 75 turn coil of wire when there are 4 amp of

current through it(fill in the blank)

4. If it takes 35 jule of energy to move a charge of 6C from one point to another what is the voltage betn the two points (fill in the blank)

5. Calculate the velocity of conductor if terminal voltage is 2.2 v/m & the magnetic field strength is 0.2T (fill in the blank)

6. Calculate the frequency of the motor if the speed is 4800 rpm & no of poles are 2(sometime speed is given in RPS)

7.What is the power in a resistance in mili volt having resistance of 12 ohm having a potential difference of 3v (fill in the blank)

8. What is the max allowable primary current of 2kva step down transformer with a 4-1 turns ratio if connected across a 440 v line (uscg optional)

9. A 40 cm wire current of 20 amp is placed in a uniform magnetic field of 0.6 the wire make an angle of 30 degree cal the magnitude of force on wire (fill in the blank)

10. Find the voltage of a motor of 200 rpm when the flux changes from 1wb to 4wb (fill in the blank)

11.Calculate avg value of 12 v peak sign wave for one complete cycle

12. Inductance or capacitance (don’t remember but the unit is same) is 6mh current go from 0.4 to 2.5 amp in 0.6 sec calculate emf (up to 3 decimal places) (fill in the blank)

13. A sine wave with RMS value of 100 V is riding on a DC level of 50 V. calculate the maximum value of the resulting wave form.

14. A half wave rectifier having a resistive load of 600 ohmwith supply voltage of 80 v and having forrowed resistanceof 100 ohm. calculate the peak current.

15.The type of the system whose transfer function is given by G(S) =(s2+3)/(s5+s4+s3+3s2+2s) is:

16.. Alfa particles enter an electromagnetic field where the electric intensity is 300v/m and the magnetic induction is 0.200T what is the velocity of alfa particles?

17.Calculate the frequency of the motor if the speed is 400 RPS and no. of poles is 2.

18.the voltage induced across a certain coil is 150 mV. A 100 ohms resistor is connected to the coil terminal. calculate the induced current in milli amps.

19. If the resistance of the wire is 15 ohms if length is doubled and dia is one third, then resistance of the wire is???

20. what is the maximum allowable primary current of a 2kva step down transformer with 4:1 turn ratio , if connected across a 440 v line?

21. If the flux through 120 turn coil changes steadily from 2wb to 6 wb in 1 second. what is the voltage induced??

22. A 20 m wire carrying a current of 10 Amps magnetic field of 0.3 T with an angle of 40 degrees with vector B. Find the magnitude of force?

23. Three resistors 40,50,60 connected in series input 30 V . Calculate voltage drop across 60 resistor.

24. The armataure resistance of a 200 V d.c. machine has 0.5 ohm. If the full load armature current is 50 A, what will be the induced e.m.f. when, the machine acts as (i) generator (ii) motor will be (a) 230 V, 170 V (b) 210 v, 190 v, (c) 225 V, 175 C (d)202.5 V, 197.5 V

25. When 3H and 2H are in series and 2H is the mutual inductance .. what is effective inductance?

FILL IN THE BLANKS1.unit of electric intensity is V/M2. PIV means Peak inverse voltage3.MCCB (protections) – Thermal protective trip4.voltage and impedence of R-L-C circuit was found by Phase diagram5.A semiconductor having no impurities and having no lattice crystalline defect is known as intrinsic semiconductor , undopped semiconductor6.At zero Kelvin the semiconductor will be an insulator7.A MCB provides protection against short circuit by using an electromagnet 8.Breakdown diode effect – (3 blanks)zener effect, avalanche effect, _-Reverse biased----------------------9.The rate of rise of current through an inductive coil is maximumAt the start of current flow

10.Diode circuit which is used to clip off signal voltage is clipper circuit11.Permanent magnets are generally made up of Alnico alloys12.The direction of induced emf can be found with the help of lenzs law13.The unit of absolute permittivity of a medium is ____FARAD/METER___________14.For a given line voltage for heating coils will produce max heat when connected in parallel15.how to check ceramic type fuse continuity test16.the direction of magnetic flux changes when direction of current changes TRUE17.the value of Vas which makes Id current approx zero is called CUT OFF voltage18.Resistance of wire is increased if the length is INCREASED and area is DECREASED19.A semiconductor is damaged by strong current because of (3 blanks)OVERHEATINGEXCESS DOPINGOVERLOAD20.Open loop transfer function of a system having one zero with positive real values is called NON MINIMUM phase21.In a control loop system having zero positive real value are called UNSTABLE22.In P-Type semiconductor the majority current carriers are HOLES23.The output frequency of a full wave rectifier is TWO TIMES the input frequency24.Breakdown diode can also be use as a VOLTAGE REGULATOR, MOTOR PROTECTION