Week 3 Homework Assignment

1. A 9.0-V battery is connected to a bulb whose resistance is 1.6W. How many electrons leave the battery per minute?
2. Estimate at what temperature copper will have the same resistivity as tungsten does at 20°C?
3. A 60-W lightbulb is normally operated at 240V. When it is operated at 120V how bright will it be relative to 10-W 120V bulbs? Estimate how much power it will consume.
4. A power station delivers 520kW of power to a factory through wires of total resistance of 3.0W.  How much less power is wasted if the electricity is delivered at 50,000V rather than 12,000V?
5. Calculate the peak voltage and peak current through an 1800-W arc welder connected to a 450-V ac line.
6. Two resistors when connected in series to a 110-V line use one fourth the power that is used when they are connected in parallel. If one resistor is 2.2kW, what is the resistance of the other?