Electric power and the energy a home uses
Grade 11 Science Worksheet - Building Confidence
Circle the best answer, or write your answer on the line.
Ari checks a heater element: 120 V across a 24 Ω resistance. How many watts does it use?
Bo checks a toaster element: 120 V across a 9.6 Ω resistance. How many watts does it use?
Esme checks a small car heater: 12 V across a 1.2 Ω resistance. How many watts does it use?
A hair dryer label reads 120 V and 1,500 W. What current does it draw from a 120 V outlet, Jun?
- 15 A, the size of the breaker
- 0.08 A, from 120 ÷ 1,500
- 12.5 A
- 180,000 A, from 1,500 × 120
A circuit has a 15 A breaker at 120 V. What is the most power it can supply before the breaker trips, Kira?
- 18,000 W
- 135 W, from 120 + 15
- 8 W, from 120 ÷ 15
- 1,800 W
Milo runs a 60 W bulb for 5.0 h. How much energy does it use?
- 12 Wh, from 60 ÷ 5.0
- 0.30 kW, a power unit for an energy
- 3.0 kWh
- 300 Wh, which is 0.30 kWh
A home uses 450 kWh in a month. How many joules is that, with 1 kWh = 3.6 × 10⁶ J, Noah?
- 1.62 × 10⁹ J
- 1.62 × 10⁶ J
- 1.62 × 10¹² J
- 1.25 × 10⁻⁴ J, from 450 ÷ (3.6 × 10⁶)
Pia compares a 100 W bulb on for 1.0 h with a 1,000 W heater on for 0.10 h. Which uses more energy?
- The heater: 1,000 Wh against 100 Wh
- The heater, since its power is ten times larger
- Neither: both use 100 Wh
- The bulb, since it runs ten times longer
Tala compares a 1,500 W heater run 4 h a day with a 150 W computer run 8 h a day, for 30 days. Which uses more energy?
- The computer, since it runs longer each day
- The heater: 180 kWh, against 36 kWh
- They use the same, since both are plugged in
- The heater: 6,000 kWh, from 1,500 × 4
Zee runs a 1.5 kW oven for 40 minutes. How much energy does it use?
- 1.5 kWh, the power as the energy
- 60 kWh, from 1.5 × 40
- 1.0 kWh
- 0.04 kWh, from 1.5 ÷ 40