A 60 W light bulb runs for 2 hours. How many joules of energy does it use?

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Multiple Choice

A 60 W light bulb runs for 2 hours. How many joules of energy does it use?

Energy used equals power times time. Since power is the rate at which energy is transferred, and 1 watt is 1 joule per second, you multiply watts by seconds to get joules. Here, the bulb is 60 W and runs for 2 hours. Convert 2 hours to seconds: 2 × 3600 = 7200 s. Then energy = 60 × 7200 = 432,000 J. So the energy used is 432,000 joules. Common checks: 216,000 J would be what you get for 60 W over 3600 s (1 hour); 720,000 J would be 60 W over 12,000 s (about 3.3 hours); 1,080,000 J would be 60 W over 18,000 s (about 5 hours).

Energy used equals power times time. Since power is the rate at which energy is transferred, and 1 watt is 1 joule per second, you multiply watts by seconds to get joules.

Here, the bulb is 60 W and runs for 2 hours. Convert 2 hours to seconds: 2 × 3600 = 7200 s. Then energy = 60 × 7200 = 432,000 J. So the energy used is 432,000 joules.

Common checks: 216,000 J would be what you get for 60 W over 3600 s (1 hour); 720,000 J would be 60 W over 12,000 s (about 3.3 hours); 1,080,000 J would be 60 W over 18,000 s (about 5 hours).

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