Multiple Choice
Four students, each with a mass of , run up a flight of stairs of height . The times taken are: Student A: s, Student B: s, Student C: s, Student D: s. Which student has the largest power output?
9. Work & Energy
Power
Multiple Choice
What does the power rating on a light bulb describe?
A
The brightness of the bulb as perceived by the human eye, measured in lumens
B
The total amount of energy the bulb will use in its lifetime, measured in (joules)
C
The maximum voltage that can be safely applied to the bulb, measured in (volts)
D
The rate at which the bulb converts electrical energy into light and heat, measured in (watts)
Verified step by step guidance1
Understand that the power rating of a light bulb indicates how much electrical energy it uses per unit time.
Recall that power is defined as the rate of energy transfer or conversion, mathematically expressed as \(P = \frac{E}{t}\), where \(P\) is power in watts, \(E\) is energy in joules, and \(t\) is time in seconds.
Recognize that the power rating tells us how quickly the bulb converts electrical energy into other forms, mainly light and heat.
Note that the power rating is measured in watts (W), which quantifies this rate of energy conversion.
Conclude that the power rating does not directly measure brightness (lumens), total energy used over lifetime (joules), or maximum voltage (volts), but rather the rate of energy use at any moment.
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