[SCEN167 logo] 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?

[Fig. 2]

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?

[Fig. 3]

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!

[Fig. 5]

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.

[Fig. 6a]

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

[Fig. 6b]

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!

[Fig. 6c]

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!


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