An electric lawn mower has a resistance of 160 ohms and draws 15A. What is the cost of operating the lawn mower for 30 minutes if electrical energy costs $0.12/kWh?
Voltage/Resistance = Current
x/160 = 15
x = (15)(160) V
Power = Current*Voltage
==> (15)(15)(16) = 3600 Watts
30 min = (30)(60) seconds
==> (3600)(30)(60) Watts for 30 min.
==> (3600)(30)(60)/(1000) = 6480 kWh
==> (6480)(.12) = $777.6