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Basic Electricity

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Basic Electricity Circuits Ohms Law and formulas Parallel circuit Current flow of a branch I branch a = E R1 I branch b = E ... – PowerPoint PPT presentation

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Title: Basic Electricity


1
Basic 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
3
Series Circuit - Single path same current flows
through each component
4
Series Circuit Laws
5
E volts Most auto techs use the letter V
The sum of the individual voltage drops in a
series circuit equals the applied voltage.
6
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)
7
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 knowNote It current Total
8
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
9
Parallel Circuit - More then one path, voltage is
the same at each branch of the circuit.
10
Parallel Circuit Laws
11
E volts In a parallel circuit, the voltage is
the same across each branch.
12
I current or amps The total current in a
parallel circuit is equal to the sum of the
individual branch currents.
13
R resistance The total resistance in a
parallel circuit is always less than the smallest
resistive branch
14
Series parallel, combination of both circuits
15
It takes one volt to push one amp though one ohm
of resistance
16
Ohms 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
17
Ohms 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
18
Series CircuitResistance TotalRt R1 R2 R3
19
R1 1002 R2 99 R3 984 Rt 2085
20
Series Circuit Current Total Et It
Rt
It Amps Total
21
Series 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
22
Series Circuit Voltage drop across each
resistorE It X R1E It X R2E It X R3
23
Series 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
24
Series 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
25
Series 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
26
Series 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

27
Parallel 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
29
Parallel circuitResistance Total if 3 or more
Resistors
1 _ 1 1
1 1 R1 R2 R3 R4
30
Rt 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 ?
31
Parallel circuitResistance Total if Resistors
are all the same value
Value of one Resistance Rt
------------------------------ Number of
Resistances
32
Parallel circuitCurrent flow
Et It Rt

33
Parallel circuitCurrent flow
Et It Rt
12V 6A 2 ?
34
Parallel circuitCurrent flowof a branch
I branch a E R1
I branch b E R2
35
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).  

36
The 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
37
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 1hp746W
    would be required for calculations.

38
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 (?) 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.

39
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.

40
The end
  • Thanks to the toolboxshop.com for the info on
    power
  • http//www.thetoolboxshop.com/guides-3-w.asp
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