Question

The potential difference across the

terminals of a battery is 8.5 V, when

a current of 5 A flows through it

from the negative terminal to the

positive terminal. When a current of

4 A flows through it in the opposite

direction, the terminal potential

difference of the battery is 10 V.

Find the emf and the internal

resistance of the battery.​

Answer 1

Answer:

Internal Resistance = 0.2

EMF of the cell, ε = 9.5

Explanation:

V = ε - Ir

Given that, V = 8.5 V and I = 5A

ε = 8.5 + 5r →→→ (1)

When the direction of current us reversed,

V = ε + Ir

Given that V = 10V and I = 2A

10 = ε + 2r

Using (1),

10 = 8.5 + 5r + 2r

10 - 8.5 = 7r

1.5 = 7r

r = 0.2

Sub r = 0.21 in (1),

ε = 8.5 + 5(0.2)

ε = 9.5