Practical Electricity, part 2 Ev I R P OHMS LAW hFE current gain Skin effect?

Practical Electricity, part 2

Ev I R POHMS LAW

hFEcurrent gain

Diodes in action

chassis

Turn Sig

chassis

chassischassis

BRAKE

TURN SIGNAL

Agenda

Voltage Current Resistance Power, Volt Amps Symbology Single Phase Three Phase

Circuits

Electric Circuits Consist of Three Parts :– 1. Power Source – Battery, Solar Cell, – 2. Conductors - Connecting Wires – 3. Load - Device such as, Motors, Lights, Heating

etc.

3.3. Load Load1.1. PowerPower SourceSource

Simplified CircuitSimplified Circuit

2. Conductors

“VOLTAGE TYPES”VOLTAGE TYPES”

STATIC

CHEMICAL

SOLAR

Squirrel Power

Voltage

Voltage (EMF Electromotive Force)– Volts (E or V) = Measurement of electrical force or

pressure. Similar to pressure. Expressed as Electromotive Force (E) or (emf) in Ohm’s Law.

Common Units: Microvolt (uV) = 1/1,000,000 Volt Millivolt (mV) = 1/1000 Volt Volt = 1 Kilovolt (kV) = 1000 Volts

“Difference of Potential”

Difference of Potential = – Is the force that causes free electrons to move

through a conductor as an electric current is referred to as difference of potential or often shortened to “potential”.

Similar to liquid flow there must be a difference in pressure or “differential pressure” or there will be no flow.

Analogy to Liquid LevelAnalogy to Liquid Level

ValveValve

Liquid Liquid PressurePressure

Difference Difference of of

PotentialPotential

LevelLevel

“Difference of Potential”

“Difference of Potential”

SwitchSwitch

LoadLoadPowerPowerSourceSource

Difference Difference of of

PotentialPotential

Tank ATank A Tank BTank B

When a difference in potential exists between two charged bodies that are connected by a conductor, electrons will

flow until the two charges are equalized.

“CURRENT”

Electric Current = – The flow of electrons through conductive

materials when electricity is being converted to useful work.

Two Electric Current Types– Direct Current (DC)– Alternating Current (AC)

“CURRENT”

Measurement of Amperage (Current Flow)– Amperes or “Amps” (A) = The measurement of current flow

through a conductor (wire). – Number of (electrons) that pass through a given point, in a

second. Expressed as Intensity (I) in Ohm’s Law

– Common Units:– = 1 Amp– Milliamp (mA) = 1/1000 Amp .001A 1

ma– Microamp (uA) = 1/1,000,000 Amp .000001A 1µa

“RESISTANCE”

Resistance (Opposition to Current Flow)– Ohm (W) = Measurement of resistance in an electrical circuit.

Similar to restriction of liquid or gas flow. Expressed as Resistance (R) in Ohm’s Law. Common Units: Ohms (W) = 1 Ohm Kilohms (k W) = 1000 Ohms Megohms (meg W) = 1,000,000 Ohms

Every load on an electrical circuit creates resistance. Resistance to the current load creates heat.

The OHM

CURRENT RATING

WIRE SIZE(known as ‘gauge’)

WIRE DIAMETER

(expressed in circular mils*)

30 Amps 10 AWG 10383

20 Amps 12 AWG 6530

15 Amps 14 AWG 4110

10 Amps 16 AWG 2580

8 Amps 18 AWG 1620

*Circular Mils = the standard unit of measurement of a round wire cross-sectional area The area in circular mils of a round conductor is obtained by squaring the diameter, measured in mils.

Ohms Per Foot

““IMPEDANCE, DC ”IMPEDANCE, DC ”

IMPEDANCE – Algebraic sum of all the Resistance in the circuit.

For DC = Z is the same as the total resistance of the circuit ( Rt )

Z

Resistance and Voltage Drop

1000 ft.1000 ft.

100 Psig100 Psig 98.36 Psig98.36 Psig

1” Pipe - 100 Psig water pressure - 1 GPM flow1” Pipe - 100 Psig water pressure - 1 GPM flow

Pressure DropPressure Drop

Voltage DropVoltage Drop

100 Volts100 Volts 98.38 Volts98.38 Volts

12 Gage Wire - 100 Volts - 1 Amp Current flow12 Gage Wire - 100 Volts - 1 Amp Current flow

1000 ft.1000 ft.

““VOLTAGE DROP”VOLTAGE DROP”

Power

In Back to the Future, Doc Emit Brown declares that it takes 1.21 gigawatts

to travel through time. The gigawatt is a unit of power, not energy.

Now, a gigawatthour is a unit of energy.

““POWER” “WATT”POWER” “WATT”

Electrical Power (Horsepower)– Watt (W) = 1 Watt = 1 Volt times 1 Amp of current

Expressed as (P) in power calculation formulas. 746 Watts = 1 Horsepower. 1 HP = ¾ KiloWatt

Common Units:1 Microwatt = 1/1,000,000 Watt1 Milliwatt = 1/1000 Watt1 Kilowatt = 1000 Watts1 Megawatt = 1,000,000 Watts1 GigaWatt = 1 Billion Million WattsKilowatt Hour = Kilowatts used in 1 hour

Review Discussion

– Voltage is a measurement of: electrical force (similar to pressure)

– Amperage is a measurement of current flow (similar to flow)

– Ohm is a measurement of resistance to current flow (similar to restriction)

– Wattage is a measurement of power used to perform work (horsepower)~

– Voltage Drop is the result of the corresponding result of opposition to current flow.

2 More Electrical Terms

Inductance (Coil, transformer) Capacitance (Capacitor)

Factors present in an AC circuit because the current is operating at 60 HZ, frequency dependant.

XL= 2π f L1

XC= 2π f C

AC Current Relationships

Current thru Resistor is in phase Current thru Inductor will lag 90 Current thru Capacitor will lead by 90 Magnitude of current thru RLC

will dependent on Impedance which is a vector sum

POWER FACTOR CORRECTION– Capacitor Banks

Resistive vs Inductive

ELI ICE MANVoltage leads Current in a inductive circuit

Current leads voltage in a capacitive circuit

Electrical Theory

Basic Formulas - Ohm’s Law Law 1 -If the voltage remains constant the

current is inversely proportional to the resistance Law 2 - If the current remains constant the

emf voltage across a device varies directly with the resistance

Law 3 - If the resistance remains constant the current varies directly with the applied voltage

V = EMF in VoltsI = Intensity in AmpsR = Resistance in Ohms

IVR

Symbols

Electrical TheoryElectrical Theory

Basic Formulas - Calculating Power– The basic formulas used for calculating power as it is

related to volts of emf, Amps of current. and resistance are contained in the following summary pie graph.

P = Power in WattsI = Intensity in AmpsV = EMF in Volts

P = I x V

IPV

Electrical TheoryElectrical Theory

Summary of Basic

Formulas

Calculate Voltage Using Ohms Law

Calculate Resistance Using Ohms Law

Calculate Current Using Ohms Law

Handout

Calculate Resistance (Handout)

Resistors in series Resistors in parallel Resistors in combination

Calculate Current

Current is same in series (Rt) Current in parallel adds (Rt)

Calculate Power

Power Adds in parallel

Voltage Drop

Symbology

           Wires, Not Connected, Crossing

           Wires, Connected, Crossing

LADDER LOGIC

ELECTRIC DRYER

BUILDINGSBLUEPRINT

Solar Cell Battery Regulator

Solar Cell Battery Regulator

AC Single Phase

AC 3 Phase

3 Coils in GeneratorCycles are 120 degrees apartA B C

A B C A

Advantages of 3 PH AC

3 or 4 Wires Depending on Load Wire is Expensive, but will be smaller

3 PH - WYE Connected Load

Power in Delta & Y Connected Systems

Power = √3 * E * I * pf DELTA Y WYE

WYE Neutral Current Occurs ONLY when Phase current is unbalanced

Battery Configurations