# 7 Physics questions: resistance, power, current, series

1. Find the resistance of a light bulb that is connected to a 120-volt line and has a current of 0.5 amps flowing through it.

2. Calculate the electrical power of a lamp that carries 2 amps of current at 120 volts.

3. A heater uses 20 amps when connected to a 100-volt line. If the electric power costs 10 cents per kilowatt hour, what is the cost of running the heater for 10 hours?

4. The current through two identical light bulbs connected in a series is 0.25 amps. The voltage across both bulbs is 100 volts. Find the resistance of a single light bulb.

5. What is the difference between series and parallel circuits? Specify in words and algebraic formula, if possible, the relationships between current, voltage, and resistance in each type of circuit.

6. Define the following terms:

a. Magnetic field

b. Electromagnet

c. Magnetic poles

d. Magnetic force

7. Describe in detail the effects of a magnetic field on a current-carrying wire.

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#### Solution Summary

Step by step solutions to all the problems are provided.

Physics Problems: Electricity, Voltage, Conductor, Resistance, Current, Power

1- ) a string of Christmas-tree lights is frequently made of miniature lamps connected in series. For an 8-lamp, 120- volt set what is the voltage across each lamp? If one lamp were removed, what would happen? The voltage across the empty socket becomes equal to the line voltage. Why is this?

2- ) a piece of copper wire is cut into 10 equal parts. These parts are connected in parallel. How will the combined resistance of the parallel combination compare with the original resistance of the single wire?

3 - ) a wire 200 cm long has a resistance of 16.0 ohms. It is connected in series with resistance box of 8.00 ohms to battery having a terminal voltage of 8.00 volts. A poorly calibrated voltmeter connected across 150 cm of the wire reads 3.84 volts. What is the percentage error of the reading of the voltmeter?

4 - ) Sketch the outline of a cube. Imagine that each of the 12 edges represents a conductor having a resistance of 1.0 ohm. What is the resistance between corners diagonally opposite each other?

5 - ) a bank of three resistors in parallel is connected in series with a 3.00 ohm resistor and a battery of negligible internal resistance. The parallel group has resistances of 5.00 , 8.00, and 12.0 ohm resistor, what must be the emf of the battery ?

6 - ) What would the resistance of a power line have to be in order that the line drop shall not exceed 2% of the rated voltage of 120 volts when the current is changed from zero to 40 amp?

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