A household device consumes 5 kWh of energy. How many joules is that?

A household device consumes 5 kWh of energy. How many joules is that?

• A. 9.0 × 10^6 J
• B. 1.8 × 10^7 J
• C. 2.5 × 10^7 J
• D. 3.6 × 10^7 J

Answer: (B)

The key idea is converting energy from kilowatt-hours to joules. A kilowatt-hour is the amount of energy used by a device at 1 kilowatt for 1 hour. In joules, that’s 1000 watts × 3600 seconds = 3.6 × 10^6 J. For 5 kilowatt-hours, multiply by 5: 5 × 3.6 × 10^6 J = 1.8 × 10^7 J. So the energy is 1.8 × 10^7 joules.

The key idea is converting energy from kilowatt-hours to joules. A kilowatt-hour is the amount of energy used by a device at 1 kilowatt for 1 hour. In joules, that’s 1000 watts × 3600 seconds = 3.6 × 10^6 J. For 5 kilowatt-hours, multiply by 5: 5 × 3.6 × 10^6 J = 1.8 × 10^7 J. So the energy is 1.8 × 10^7 joules.