Title: Basic Electricity
1Basic Electricity
- Circuits
- Ohms Law and formulas
2(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
3Series Circuit - Single path same current flows
through each component
4Series Circuit Laws
5E volts Most auto techs use the letter V
The sum of the individual voltage drops in a
series circuit equals the applied voltage.
6Two 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)
7I 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 knowNote It current Total
8R resistance Individual resistance in a
series circuit add up to the total circuit
resistance. Rt R1 R2 R3 Terms to know Rt
Resistance Total
9Parallel Circuit - More then one path, voltage is
the same at each branch of the circuit.
10Parallel Circuit Laws
11E volts In a parallel circuit, the voltage is
the same across each branch.
12I current or amps The total current in a
parallel circuit is equal to the sum of the
individual branch currents.
13R resistance The total resistance in a
parallel circuit is always less than the smallest
resistive branch
14Series parallel, combination of both circuits
15It takes one volt to push one amp though one ohm
of resistance
16Ohms Law
Amperes I - Intensity Volts E -
Electromotive force Ohms R -
Resistance
- to find
- E I x R
- I E R
- R E I
E
I x R
17Ohms Law For Auto techs
Amperes A - Amperage Volts V -
Voltage Ohms R - Resistance
- to find
- V A x R
- A V R
- R V A
V
A x R
18Series CircuitResistance TotalRt R1 R2 R3
19R1 1002 R2 99 R3 984 Rt 2085
20Series Circuit Current Total Et It
Rt
It Amps Total
21Series Circuit Current TotalExample
R2 2 ?
R1 2 ? R2 2 ? R3 2 ? Rt 6 ? V or E 12
R1 2 ?
R3 2 ?
Et 12 2 It Rt 6
12V
22Series Circuit Voltage drop across each
resistorE It X R1E It X R2E It X R3
23Series Circuit Current TotalExample Finding Volts
R2 2 ?
R1 2 ? R2 2 ? R3 2 ? Rt 6 ?
R1 2 ?
R3 2 ?
It X R1 E 2 X 2 4 It X R2 E 2 X 2
4 It X R3 E 2 X 2 4 444 12 Volts
It 2
24Series Circuit Current TotalExample 2
R2 4 ?
R1 2 ? R2 4 ? R3 6 ? Rt 12 ?
R1 2 ?
R3 6 ?
It X R1 E 1 X 2 2 It X R2 E 1 X 4
4 It X R3 E 1 X 6 6 246 12 Volts
12V
It 1
Et 12 1 It Rt 12
25Series Circuit Voltage drop across each
resistor
R2 4 ?
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 ?
R3 4 ?
12V
26Series Circuit Voltage drop across each resistor
- If there are only 2 resistors and they are the
same size just take voltage divide by 2 and you
have voltage drop V 2 - Any number of Resistors all the same size. V
of Resistors Voltage Drop
27Parallel circuitResistance Totalif only 2
Resistors
R1 x R2 Rt -----------
R1 R2
28 R1 x R2 Rt ----------- R1
R2
R1 2 ?
2 X 4 8 Rt 1.33
-------------- 2 4 6
R2 4 ?
Note Rt is less the Smallest resistor
29Parallel circuitResistance Total if 3 or more
Resistors
1 _ 1 1
1 1 R1 R2 R3 R4
30Rt if 3 or more Resistors
1 _ 1 1
1 R1 R2 R3
R1 2 ?
1 _ 1 1
1 2 4 6
1_ .917
1 .5 .25 .167
R2 4 ?
R3 6 ?
Rt 1.09 ?
31Parallel circuitResistance Total if Resistors
are all the same value
Value of one Resistance Rt
------------------------------ Number of
Resistances
32Parallel circuitCurrent flow
Et It Rt
33Parallel circuitCurrent flow
Et It Rt
12V 6A 2 ?
34Parallel circuitCurrent flowof a branch
I branch a E R1
I branch b E R2
35The 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).
36The Power Triangle
- Power Current x Voltage
- P A x V
- Current Power over Voltage
- A P V
- Voltage Power over Current
- V P A
P
A x V
37The 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 1hp746W
would be required for calculations.
38The 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 (?) 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.
39The 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.
40The end
- Thanks to the toolboxshop.com for the info on
power - http//www.thetoolboxshop.com/guides-3-w.asp