Question

1. How much does it cost to operate a 120-W lightbulb for 25 min if the cost of electricity is $0.086 per kilowatt-hour?

2. A 75-V battery supplies 3.9 kW of power. How much current does the battery produce? Express your answer to two significant figures and include the appropriate units.

3. A battery connected to a 140-? resistor dissipates 2.5 W of power. If the circuit contains only the battery and the resistor, what is the voltage of the battery? Express your answer to two significant figures and include the appropriate units.

4. A resistor carries a current of 2.2 A and dissipates 15 W of power. What is the resistance of the resistor? Express your answer to two significant figures and include the appropriate units.

5. A current of 2.1 A flows through an 85-? resistor. How much power is dissipated? Express your answer to two significant figures and include the appropriate units.

*if you could provide the work and formulas for the problems, that would really help me understand the concept!

Answer 1

1. Power used by bulb in 25 minute= 120*25=3000W-min =50W-hr = 0.05kW-hr

cost

2. Power

3. Power

4. Power

5. Power