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Electric Power
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Answer Me!!!
How is the brightness of a light bulb measured? What do you think is the significance of this?
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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.
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Electrical Power
Electric power is the product of electric current and potential difference
P = V·I Power is still measured in Watts:
watt1second
Joule11ampere1volt
second
Coulomb1
Coulomb
Joule11ampere1volt
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Electrical Power and Ohm’s Law
R
VRIVIP
22
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Electrical Energy
Since work is define by:
Electrical energy is measured in Joules. Energy is a scalar quantity.
R
tVRtIVItW
PtW2
2
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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?
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Practice Problem 2
If the potential drop across an operating 300 W floodlight is 120 V, what is the current through the floodlight?
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Practice Problem 3
A potential drop of 50 V is measured across a 250 ohm resistor. What is the power developed in the resistor?
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Practice Problem 4
As the potential difference across a given resistor is increased, the power expended in moving the charge through the resistor will _____________.
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Practice Problem 5
A toaster dissipates 1500 W of power in 90 seconds. What is the amount of electric energy used by the toaster?
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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?
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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?
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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?