AP Physics 1 Question 369: Answer and Explanation
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7. A circuit consists of a 500 Ω resistor connected to a variable voltage source. The voltage is increased linearly from 0 V to 5 V over a period of 20 s, as shown in the graph above. Which of the following graphs corresponds to the power dissipated by the resistor as a function of time?
Correct Answer: D
At 20 s, the voltage across the resistor is 5 V, so the current is
The power at this time is given by
P = IΔV = (0.01 A)(5 V) = 0.05 W
The shape of the graph can be obtained by combining these two equations:
which shows that the power dissipated by the resistor will increase quadratically with the voltage.