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