# SCEN167 Midterm Exam

March 19,1996

1. (3 pts.)

List three significant observations that we made from the Play-Doh experiments that we performed in class:

2. (4 pts.)

What value must R have to produce 10 A current through the battery?

3. (4pts.)

Evaluate the current that will flow through the fuse if all three appliances operate at full power at the same time. Will the fuse "blow" or not?

4. (2 pts.)

Why is common household wiring primarily ac rather than dc?

Why are common batteries dc and not ac?

5. (4 pts.)

Construct a circuit from the following components to determine experimentally the internal resistance of the 1.5 V battery. Draw connecting wires!

Assume a reading for the voltmeter (that is, make up a value!) and determine the internal resistance of the battery by applying Ohm's law.

6. (3 pts.)

Consider these circuits constructed from resistors and a real battery. Do not assign numerical values to the resistances! -- answer the questions in words through careful reasoning.

In circuit (a) the resistor is dissipating a certain amount of power...

When resistor R2 is added to the circuit as in (b), in series with R1, does the power dissipated by R1 increase, decrease, or stay the same? Explain!

When resistor R3 is added to the circuit as in (c), in parallel with R1, does the power dissipated by R1 increase, decrease, or stay the same? Explain!