A cell of internal resistance 1Ω supplies current to an external resistor of 3Ω. The efficiency of the cell is?

A. 25%
B. 33%
C. 50%
D. 75%

Correct Answer:

Option D – 75%

Explanation

Efficiency = Output/input x 100/1
Efficiency = 3/(3+1) x 100/1
= 3/4 x 100/1 = 75%