Unit 4: Electric Circuits
Physics C: E&M · Unit 4 · Paper 3

Electric Circuits unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 17 terms and is the same for everyone, so a teacher can assign “Unit 4, Paper 3” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 37 min 34 points0/17 attempted
1

Power supplied vs dissipated

2

Sign conventions in the loop rule

3

Ammeter and voltmeter placement

4

Real vs ideal battery

5

Kirchhoff's rules

6

Number of independent equations

7

When reduction fails

8

Ohm's law and its limits

9

Non-ohmic devices

10

Internal resistance

11

Resistivity and resistance

12

Power dissipation

Short answer 1. Define or explain: Brightness of bulbs

3 pts

Short answer 2. Define or explain: Reducing a network

3 pts

Short answer 3. Define or explain: Current density and drift velocity

3 pts

Short answer 4. Define or explain: Maximum power transfer

3 pts

Free response

10 pts

EXPERIMENTAL DESIGN AND ANALYSIS (Question 3, 10 points). In Experiment 1, students must use a graph to determine the resistivity ρ1 of a cylindrical circuit element of uniform resistivity connected to a variable power supply (Figure 1). Available: a voltmeter, an ammeter, and a ruler. For C–D (Experiment 2): students determine the resistivity ρ2 of solid cylindrical resistors of the same material but different lengths L, each with cross-sectional area 5.0×10⁻⁶ m². The resistance R between the ends of each resistor is measured directly. Table 1: L = 0.010, 0.020, 0.030, 0.040, 0.050 m with R = 0.90, 1.6, 2.5, 3.2, 4.0 Ω.

A. Describe a procedure for collecting data that would allow the students to use a graph to determine ρ1, including steps to reduce experimental uncertainty.

B. Describe how the collected data could be graphed and analyzed to determine ρ1.

C(i). Indicate two quantities (from Table 1 or calculated) to graph for a straight line usable to determine ρ2, naming each axis. C(ii). Create the graph: recorded values, labeled axes with units, plotted points. C(iii). Draw a best-fit line.

D. Using the best-fit line from part C(iii), calculate an experimental value for ρ2.