A certain voltmeter has an internal resistance of 10,000 $\Omega$ and a range from 0 to 12 V.To extend its range to 120 V, use a series resistance of:
A)1,111 $\Omega$
B)90,000 $\Omega$
C)100,000 $\Omega$
D)108,000 $\Omega$
E)120,000 $\Omega$

Question

Quizplus · Accepted Answer

To extend the voltmeter's range to 120 V, the total resistance needed is 10 times the original since the range is being increased by a factor of 10 (from 12 V to 120 V). The voltmeter's internal resistance is 10,000 ohms. To find the series resistance required, we use the formula for total resistance in a series circuit: $R_{total} = R_{voltmeter} + R_{series}$. Since $R_{total}$ needs to be 10 times $R_{voltmeter}$ to increase the range by a factor of 10, $R_{total} = 10 \times 10,000\ \Omega = 100,000\ \Omega$. Subtracting the internal resistance of the voltmeter, $R_{series} = 100,000\ \Omega - 10,000\ \Omega = 90,000\ \Omega$.

A Certain Voltmeter Has an Internal Resistance of 10,000 Ω\OmegaΩ And a Range from 0 to 12 V

A Certain Voltmeter Has an Internal Resistance of 10,000 $\Omega$ And a Range from 0 to 12 V