Problem Solving - Electricity, Power, Resistance, Voltage, Current

1. The heating element in the rear-window defroster of a Ford automobile has a resistance of 3.00 ohms. The element is connected directly across the car's 12.0 V battery.
a) how much heat (in Joules) is produced in the element in 10.0 min?
b) how many grams of ice at 0o C can be melted?

2. How many 100 W light bulbs can be turned on in a household circuit (120 V) before tripping a circuit breaker of 15 A?

3. An Eveready flashlight is powered by a 1.5 V battery that delivers a power of 3.0 W.
a) find the battery's loss of chemical energy during the 20.0 min.
b) where did the battery's energy go?

4. A transistor radio operates by means of a 9.0 V battery that supplies it with 50 mA of current. The battery has a life of 300 hours and costs $2.00.
a) what is the dollar cost per kilowatt-hour ($/kW-h)
b) if Niagara Mohawk charges $0.10 per kW-h, how much does it cost to operate the radio using household current?
c) compare the costs in a ratio of battery/household current.

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