Question

The electromotive force of a primary cell is 2 volts. When it is short-circuited it gives a current of 4 amperes. Its internal resistance in ohms is

• A. 0.5
• B. 5.0
• C. 2.0
• D. 8.0

Answer 1

Answer: (A)

0.5

Answer 2

$E = V + i r$

After short-circuiting,

$r = \frac { E } { i } = \frac { 2 } { 4 } = 0.5 \Omega$