A microwave oven has a power requirement of 1248 W. A frozen dinner requires 6.9 min to heat on full power.
(a) How much electrical energy (in kWh) is used?
(b) If the cost of electricity is 12 cents per kWh, how much does it cost to heat the dinner?
look at the units
electrical energy (in kWh) = power (in kW) x time (in hour)
cost of electricity = [electrical energy (in kWh)]*(12 cents/ kWh)
1.72
To solve this problem, we need to use the formula for electrical energy:
Energy (in kWh) = Power (in watts) x Time (in hours) / 1000
(a) Let's calculate the electrical energy used by the microwave oven:
Power = 1248 W
Time = 6.9 minutes = 6.9/60 hours (since 1 hour = 60 minutes)
Energy (in kWh) = (1248 W) x (6.9/60 hours) / 1000
= 0.14352 kWh
Therefore, the microwave oven uses approximately 0.14352 kWh of electrical energy.
(b) To calculate the cost of heating the dinner, we need to multiply the energy usage by the cost per kWh.
Cost = Energy (in kWh) x Cost per kWh
Given that the cost per kWh is 12 cents, which is equivalent to 0.12 dollars:
Cost = 0.14352 kWh x $0.12/kWh
= $0.01722
Therefore, it would cost approximately $0.01722 to heat the dinner.