Question

If the voltage across a circuit of constant resistance is doubled, the power dissipated by that circuit will

A) decrease to one-fourth the original power.

B) be two times as large.

C) decrease to one-half the original power.

D) be four times as large.

Answer 1

Answer:

D) be four times as large.

Explanation:

The power dissipated is the product of the potential difference between the terminals and the current intensity that passes through the device:

$P=VI$

In this case, the device is a resistor. Therefore, from ohm's law:

$V=IR\\I=\frac{V}{R}$

Finally, we obtain the relation between power and voltage:

$P=\frac{V^2}{R}$

We have $V'=2V$:

$P'=\frac{V'^2}{R}\\P'=\frac{(2V)^2}{R}\\P'=4\frac{V^2}{R}\\P'=4P$

So, the power dissipated by that circuit will be four times as large.