A $7.0 - \Omega$ resistor is connected across the terminals of a battery having an internal emf of $10 \mathrm {~V}$. If $0.50 - \mathrm { A }$ current flows, what is the internal resistance of the battery?
A) $20 \Omega$
B) $13 \Omega$
C) $27.0 \Omega$
D) $10.8 \Omega$

Question

Quizplus · Accepted Answer

The total voltage is 10 V and the current is 0.5 A, so the total resistance is $ V/I = 10/0.5 = 20 \Omega $. The internal resistance is the total resistance minus the external resistance: $ 20 \Omega - 7 \Omega = 13 \Omega $.

A 7.0−Ω7.0 - \Omega7.0−Ω Resistor Is Connected Across the Terminals of a Battery Having

A $7.0 - \Omega$ Resistor Is Connected Across the Terminals of a Battery Having