Question

When a resistance of 2 ohm is connected across the terminals of a cell, the current is 0.5 A. When the resistance is increased to 5 ohm, the current is 0.25 A. The e.m.f. of the cell is

• A. 1.0 V
• B. 1.5 V
• C. 2.0 V
• D. 2.5 V

Answer 1

Answer: (B)

1.5 V

Answer 2

Since we get

$0.5 = \frac { E } { 2 + r }$ ......(i)

$0.25 = \frac { E } { 5 + r }$ .....(ii)

Dividing (i) by (ii), we get

$2 = \frac { 5 + r } { 2 + r }$ ⇒ $r = 1 \Omega$

∴ $0.5 = \frac { E } { 2 + 1 }$ ⇒