1. ELECTRIC ENERGY AND ELECTRIC POWER
Sumber Gambar : Dosen Killer
Created by Jamari, S.Pd.

2. ELECTRIC ENERGY
Energy produced from the current of electric charges in a certain closed electric cercuit is called electric energy A B I C V
W = Q V
Where :
Q = electric charges (Coulomb)
V = voltage ( volt)
W = electric energy ( joule )

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ELECTRIC ENERGY
W = Q V
Where :
t = time (sekon)
I = electric current ( Ampere)
W = V I t
because Q = I x t
because V= I R
because I= V/ R
R= electric resistance (Ohm)
V= electric voltage ( Volt)
Hal.: 3
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4. Electric energy is depended
votage (V)
W = V I t
Electric energy is depended
Electric current (I)
time (t) A B C I V

5. Daya Listrik A B C I
The amount of electric energy used by a certain electric device per unit of time is called electric power V
Where :
W = electric energy ( Joule)
t = time ( sekon)
P = electric power ( Joule/sekon = watt)

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Electric Power
Hal.: 6
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7. Electric Power 11 watt.220 V What is the meaning ?
The lamp will be ligting well if the lamp connected by voltage 220 volt
The lamp will use electric power 11 watt if the lamp connected by voltage 220 volt
Electric resistance of the lamp is
If the lamp is connected by voltage 110 volt, What is the electric power used by the lamp ?

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Electric Power
60 watt.220 V
110 V
Hal.: 8
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9. The Relation of Energy and Power Units
In SI unit system, electric power is expressed in watt
W = P x t
The table of units
Power (P)
time (t)
Energy (W)
Watt
Second
Joule (J)
watt
hour
watt.hour (Wh)
1000 Wh= 1 kWh
1Wh= 1watt seconds = 3600 joule
Hal.: 9
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10. The Equivalence of Heat with Electric Energy=
Heat
Where
Q = heat (joule)
m = mass of substance (kg) W = Q
c = specific heat of substance (J/kgo C)
P t =
m c T
T = temperature change of
substance (o C)
V i t =
m c T
I2 R t =
m c T =
m c T
Hal.: 10
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11. Efficiency of Electric Heater ()
Electric Energy
Electric
heater
Heat(Q)
W = V x I x t
W = I2 x R x t
W = V2 x t / R
Wastage energy
atau
Hal.: 11
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12. Sample Problem 1) Solution 110 V
Calculate the energy used in 3 hours !
80 watt.220 V
Solution
Power used by the lamp
110 V
Energy used by the lamp
W = P.t = 20 watt x seconds = 2,16 x 105 joule
Hal.: 12
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Sample Problem 2)
Electric
heater
Calculate the electric energy which is used by the heater in 2 hours?
I = 2 A
5 k
Solution
Hal.: 13
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Sample Problem 3)
450 watt,
110 volt
A family use electricity from PLN as much as 450 watt with voltage 110 volt. if for the lighting they use 90 watt, 220 V lamps, then calculate :
Maximum sum of lamps wich can be set
Cost for 3 lamps in one month if the lamps are used 6 hours per day ( Rp /kWh)
Hal.: 14
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Sample Problem
Soultion
a. Maximum sum of lamps
Therefore, the maximum sum of lamps is
Hal.: 15
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Sample Problem
b. Cost of 3 lamps
Energy used by 3 lamps in 1 month
W = P . t = 3. 22,5 watt.30.6 jam
= Wh = 12,15 kWh
The cost of 3 lamps is
12,15 kWh x Rp. 100,00/kWh
= 1.215,00
Hal.: 16
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