Electric Power - Camden Central School
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Transcript Electric Power - Camden Central School
Electric Power
Answer Me!!!
How is the brightness of a light bulb
measured? What do you think is the
significance of this?
Electric Power
Power is the rate at which work is done or
energy is expended.
Electrical Power is the rate at which
electrical energy is expended.
Electrical Power
Electric power is the product of electric current
and potential difference
P = V·I
Power is still measured in Watts:
1volt 1ampere
1
Joule
Coulomb
1volt 1ampere
1
Joule
second
1
Coulomb
second
1 watt
Electrical Power and Ohm’s Law
P VI I R
2
V
2
R
Electrical Energy
Since work is define by:
W Pt
2
W VIt I Rt
2
V t
R
Electrical energy is measured in Joules.
Energy is a scalar quantity.
Practice Problem 1
A microwave oven operating at 120 V is
used to heat a hot dog. If the oven draws
12.5 A of current for 45 seconds, what is
the power dissipated by the oven?
Practice Problem 2
If the potential drop across an operating
300 W floodlight is 120 V, what is the
current through the floodlight?
Practice Problem 3
A potential drop of 50 V is measured
across a 250 ohm resistor. What is the
power developed in the resistor?
Practice Problem 4
As the potential difference across a given
resistor is increased, the power expended
in moving the charge through the resistor
will _____________.
Practice Problem 5
A toaster dissipates 1500 W of power in 90
seconds. What is the amount of electric
energy used by the toaster?
Practice Problem 6
An electric iron operating at 120 V draws
10 A of current. How much heat energy is
delivered by the iron in 30 seconds?
Practice Problem 7
An electric dryer consumes 6.0 x 106 J of
energy when operating at 220 V for 30
minutes. During operation, the dryer
draws how much current?
Practice Problem 8
An operating electric heater draws a
current of 10 A and has a resistance of 12
ohms. How much energy does the heater
use in 60 seconds?