AP Physics C E and M 11.3: Electrical Characteristics

Describe the electrical characteristics of circuit elements by relating current, potential difference, resistance, and the element’s physical behavior.

[Maximum number: 2]

In Experiment 1, students are asked to use a graph to determine the resistivity $\rho_{1}$ of a circuit

element that is connected to a variable power supply, as shown in Figure 1. The circuit element

is cylindrical and has uniform resistivity. The students have access to a voltmeter, an ammeter,

and a ruler.

Figure 1

Describe how the collected data could be graphed and how that graph would be analyzed to

determine $\rho_{1}$ .

For indicating quantities that can be graphed appropriately to determine $\rho_{1}$ , consistent with the procedure from part A, such as potential difference as a function of current. — Point B1

Scoring Notes:
- Responses that include the reciprocals of the preceding example, in addition to other equivalent graphs, also earn this point.
- This point may be earned independently of the response in part A.

For a correct analysis of the graph, consistent with the first point of part B. — Point B2

Example Response
Graph the potential difference across the circuit element as a function of the current in the circuit element. Use the slope of the graph, which is $\frac{\rho_{1}l}{\pi r^{2}}$ , where l is the length of the circuit element and r is equal to the radius of the circuit element, to determine $\rho_{1}$ .

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11.3.B—Describe the electrical characteristics of elements of a circuit question 1