AP Physics C: Electricity & Magnetism 11.3 B Describe the Electrical Characteristics of Elements of a Circuit Questions

Describe circuit elements by relating current, potential difference, and resistance, and determine resistance from measurements and linear graphs.

Exam points

apply Ohm's law to calculate the current, potential difference, or resistance of a circuit element
choose current and potential difference axes that produce a linear graph for an ohmic circuit element
draw and use a best-fit line to determine resistance from its slope or the reciprocal of its slope
distinguish an ohmic element's constant resistance from non-ohmic behavior using current-voltage data

[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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AP Physics C: Electricity & Magnetism 11.3 B Describe the Electrical Characteristics of Elements of a Circuit Questions question 1