If a lamp transforms 120 joules of energy into light and heat every 2 seconds, how much power does it use?
A. 240 W
B. 480 W
C. 120 W
D. 60 W
Answer (2)
The power used by the lamp is calculated to be 60 watts, using the formula for power. By dividing the energy of 120 joules by the time of 2 seconds, we find that it consumes 60 watts. Therefore, the correct answer is D. 60 W.
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Power is defined as the rate of energy transfer, given by P = t E .
Substitute the given values: E = 120 joules and t = 2 seconds.
Calculate the power: P = 2 120 = 60 watts.
The power used by the lamp is 60 W .
Explanation
Understanding the Problem We are given that a lamp transforms 120 joules of energy into light and heat every 2 seconds. We need to find the power the lamp uses.
Defining Power Power is the rate at which energy is transferred or converted. It is measured in watts (W), where 1 watt is equal to 1 joule per second. The formula for power is: P = t E where:
P is the power in watts,
E is the energy in joules, and
t is the time in seconds.
Calculating Power We are given that the lamp transforms 120 joules of energy ( E = 120 joules) every 2 seconds ( t = 2 seconds). Substituting these values into the formula, we get: P = 2 seconds 120 joules = 60 watts Therefore, the power used by the lamp is 60 watts.
Final Answer The lamp uses 60 watts of power. This means that it converts 120 joules of energy into light and heat every 2 seconds.
Examples
Understanding power consumption is crucial in everyday life. For instance, when choosing between different light bulbs, knowing the power each uses helps you estimate electricity costs. A lower power rating means less energy consumption for the same amount of light, saving money and reducing environmental impact. This concept extends to all electrical appliances, from refrigerators to televisions, making power calculations essential for energy-efficient living.
