Examples
1. Assume that a battery rating is given in ampere-hours (A-h). What quantity is being measured?
2. When you operate a flashlight, what is being used up: battery current, voltage, energy, power, or resistance?
3. One terminal of a car battery, usually the negative, is said to be connected to "ground." Since this cannot be the actual ground, what is meant by this expression?
4. Can a copper wire and an aluminum wire of the same length have the same resistance?
5. Assume you have a rectangular solid made of carbon. It has sides of length a, 2a, and 3a. How would you connect the sires from a battery in order to obtain
a. The least resistance
b. The greatest resistance
6. The equation P = V2/R indicates that the power dissipated in a resistor decreases if the resistance is increased.
The equation P = I2R implies that the opposite is true.
Explain why there is no contradiction.
7. You may have noticed that light bulbs almost always fail just as they are turned on and not after they have been on for a period of time. Why does this happen?
8. A 15-A fuse blows repeatedly. Why is it dangerous to replace this fuse with a 25-A fuse?
Electric Current, Resistance, Ohm's Law
1. A current of 1.30 A is flowing in a wire. How many electrons are flowing past any point in the wire per second?
2. A battery ischarged with a current of 6.7 A for 5.0 h. How much charge passes through the battery?
Resistivity
3. Given a 1.00 m length of tungsten wire with a resistance cof 0.32 W. What is the diameter of the wire?
Electric Power
4. Assume that the heating element of an electric oven is designed to produce 3.3 kW of heat when connected to a 240-V source. What must be the resistance of the heating
element?
Alternating Current
5. What is the peak current in a 2.2 kW resistor connected to a 220-V rms ac source?