Post on 13-Jan-2016
transcript
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Basic Electricity
Circuits
Ohms Law and formulas
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(I or A) Current ‑ Flow of electrons through a conductor as a result of pressure applied ‑I‑ Intensity -A- Amperage
(E or V) Voltage ‑ Force or electrical pressure that moves electrons ‑E‑ Electromotive force -V- Voltage
(R) Resistance ‑ Opposition to current flow or electrical restriction
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Series Circuit ‑ Single path same current flows through each
component
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Series Circuit Laws
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E = volts Most auto techs use the letter V
The sum of the individual voltage drops in a series circuit equals the
applied voltage.
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Two Definitions you will need to know when dealing with voltage.Open Circuit Voltage or OCVVoltage when no load is applied to the car. Applied Voltage Voltage when a load is applied to the car. (Headlights are on)
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I = current or amps Most auto techs use the letter A
In a series circuit, the current flowing in the circuit is the same
at any point.Terms to know
Note It = current Total
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R = resistance Individual resistance in a series circuit add up to the total circuit resistance.
Rt = R1 + R2+ R3
Terms to know
Rt = Resistance Total
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Parallel Circuit ‑ More then one path, voltage is the same at each
branch of the circuit.
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Parallel Circuit Laws
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E = volts In a parallel circuit, the voltage is the same across
each branch.
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I = current or amps The total current in a parallel circuit is
equal to the sum of the individual branch currents.
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R = resistance The total resistance in a parallel circuit is
always less than the smallest resistive branch
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Series parallel, combination of
both circuits
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It takes one volt to push one amp though one ohm of resistance
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Ohm’s Law
to find E = I x R
I = E ÷ R
R = E ÷ I
E
I x R
Amperes = I - Intensity
Volts = E - Electromotive force
Ohms = R - Resistance
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Ohm’s Law For Auto techs’
to find V = A x R
A = V ÷ R
R = V ÷ A
V
A x R
Amperes = A - Amperage
Volts = V - Voltage
Ohms = R - Resistance
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Series CircuitResistance TotalRt = R1 + R2+ R3
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R1 = 1002R2 = 99R3 = 984Rt = 2085
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Series Circuit Current Total
Et It= Rt
It = Amps Total
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R1= 2 ΩR2= 2 ΩR3= 2 ΩRt= 6 Ω
V or E = 12
Et 12 2 It= Rt 6
R1 = 2 Ω
R2 = 2 Ω
R3 = 2 Ω
Series Circuit Current TotalExample
12V
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Series Circuit Voltage drop across each resistor
E= It X R1
E= It X R2
E= It X R3
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R1= 2 ΩR2= 2 ΩR3= 2 ΩRt= 6 Ω
R1 = 2 Ω
R2 = 2 Ω
R3 = 2 Ω
Series Circuit Current TotalExample Finding Volts
It X R1 = E2 X 2 = 4It X R2 = E 2 X 2 = 4It X R3 = E2 X 2 = 44+4+4= 12 Volts
It = 2
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R1= 2 ΩR2= 4 ΩR3= 6 ΩRt= 12 Ω
R1 = 2 Ω
R2 = 4 Ω
R3 = 6 Ω
Series Circuit Current TotalExample 2
It X R1 = E1 X 2 = 2It X R2 = E 1 X 4 = 4It X R3 = E 1 X 6 = 62+4+6 = 12 Volts
It = 1
12V
Et 12 1 It= Rt 12
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Series Circuit Voltage drop across each resistor
To find Voltage drop across each resistor you first must find It . Take Voltage (12) and divide by Rt Which is 10 the answer is 1.2 = It
Then take It X R1 = Voltage drop of R1
1.2 X 2 = 2.4
It X R2 = Voltage drop of R2
1.2 X 4 = 4.8
It X R3 = Voltage drop of R3
1.2 X 4 = 4.8 2.4 + 4.8 + 4.8 = 12
R1 = 2 Ω
R2 = 4 Ω
R3 = 4 Ω
12V
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Series Circuit Voltage drop across each resistor
• If there are only 2 resistor’s and they are the same size just take voltage divide by 2 and you have voltage drop V ÷ 2
• Any number of Resistor’s all the same size. V ÷ # of Resistor’s = Voltage Drop
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R1 x R2
Rt = ----------- R1 + R2
Parallel circuitResistance Total
if only 2 Resistors
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R1 x R2
Rt = ----------- R1 + R2
R2 = 4 Ω
R1 = 2 Ω
2 X 4 = 8Rt 1.33 = -------------- 2 + 4 = 6
Note Rt is less the Smallest resistor
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Parallel circuitResistance Total
if 3 or more Resistors
1 _ 1 1 1 1 R1+ R2+ R3+ R4
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Rt if 3 or more Resistors 1 _ 1 1 1 R1+ R2+ R3
R1 = 2 Ω
R2 = 4 Ω
R3 = 6 Ω
1 _ 1 1 1 2 + 4 + 6
1 .5 + .25 + .167
1_ .917
Rt = 1.09 Ω
==
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Parallel circuitResistance Total
if Resistors are all the same value
Value of one Resistance Rt= ------------------------------ Number of Resistances
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Parallel circuitCurrent flow
Et It= Rt
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Parallel circuitCurrent flow
Et It= Rt
12V 6A = 2 Ω
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Parallel circuitCurrent flowof a branch
I branch a = E R1
I branch b = E R2
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The Power Triangle or Joules Law
• For calculating using
• Power (W) Current (A) and voltage (V)
• Used in the same way as the Ohms Law triangle we can use the same method to see the relationship between power (W), current (A) and Voltage (V).
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The Power Triangle• Power = Current x Voltage
• P = A x V
• Current = Power over Voltage
• A = P ÷ V
• Voltage = Power over Current
• V = P ÷ AP
A x V
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The Power Triangle
• P = Watts
• Horsepower (hp) Some electrical devices such as electric motors have a power (W) rating in horsepower to which a conversion of 1hp=746W would be required for calculations.
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The history of the terminology • Each of the units of measurement are named after famous experimenters in
electricity and energy
• Voltage, Volts (V) named after the Italian Alessandro Volta known especially for the development of the first electric cell or modern translation "the battery" in 1800.
• Amps (A) named after the Frenchman Andre M.Ampere one of the main discoverers of electromagnetism.
• Ohms (Ω) named after the German Georg Simon Ohm a physicist who began his research with the recently invented electrochemical cell (invented by the Italian Alessandro Volta). Using equipment of his own creation, Ohm determined that there is a direct proportionality between the potential difference (Voltage) applied across a conductor and the resultant electric current now known as Ohms Law.
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The history of the terminology • Each of the units of measurement are named after famous experimenters in
electricity and energy
• Watts (W) named after the Scotish inventer and mechanical engineer James Watts who's name was adopted as a measurement by the second congress of the British association for the advancement of science in 1889.
• Joule (J) named after the English physicist James Prescott Joule in recognition of his work on heat and it's relationship to mechanical work or energy.
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The end
Thanks to the toolboxshop.com for the info on power
http://www.thetoolboxshop.com/guides-3-w.asp