Question

A 50V battery is connected across a 10 ohm resistor. The current is 4.5 amperes. The internal resistance of the battery is

• A. Zero
• B. 0.5 ohm
• C. 1.1 ohm
• D. 5.0 ohm

Answer 1

Answer: (C)

1.1 ohm

Answer 2

$i = \frac { 50 } { R + r }$ ⇒ $r = \frac { 50 } { 4.5 } - 10 = \frac { 5 } { 4.5 } = 1.1 \Omega$