AnswersPhysicsElectricity Use in Homes and Businesses

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How does the energy used by a 100 cap w lightbulb compare with the energy used by a 40 cap w lightbulb in a given amount of time?

A
The 100 cap w bulb uses 60 times more energy.
B
The 100 cap w bulb uses 2 point 5 times more energy.
C
The 40 cap w bulb uses 60 times more energy.
D
The 40 cap w bulb uses 2 point 5 times more energy.
5

Compact fluorescent lightbulbs (CFLs) cost more than incandescent lightbulbs and have lower wattages than incandescent bulbs. Which statement best describes why a homeowner would choose to pay the extra money for the CFLs?

A
CFLs use more energy as a result of the lower wattages, but electric companies charge less for energy used in CFLs.
B
CFLs will cost less to run in the long term because they are brighter and would need to be on for fewer hours.
C
CFLs use the same amount of energy as incandescent lights, but they last much longer and do not need to be replaced as often.
D
CFLs will cost less to run in the long term because they use less energy than the incandescent bulbs as a result of the lower wattage.
6

What do hydroelectric plants use to generate electrical energy?

A
natural gas
B
falling water
C
fission of uranium
D
wind
7

Gina examines the equations for electric power and Ohm's law. She thinks that there is a third equation that can calculate power using only voltage and resistance. Which statement best evaluates Gina’s idea?

A
It is incorrect, because both equations for power use current.
B
It is correct, because cap i is equal to cap v over cap r .
C
It is incorrect, because Ohm’s law does not include cap i squared .
D
It is correct, because cap i is equal to cap r over cap v .
9

What is the unit for electrical power?

A
joule (J)
B
volt (V)
C
kilowatt-hour (kWh)
D
watt (W)
10

What is the rate at which electrical energy is converted into other forms of energy?

A
electrical resistance
B
electric current
C
electrical power
D
energy efficiency

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