Question

A resistor of 10 ohms connected across a cell of emf 12v draws the current of 1.1

a. find the internal resistance of a cell

Answer 1

From Ohm’s Law

i = E / (R + r)

1.1 = 12 / (10 + r)

11 + 1.1r = 12

1.1r = 1

r = 1 / 1.1

r = 10/11 Ω

∴ Internal resistance of battery is 10/11 Ω

Answer 2

Ohm’s Law

i = E / (R + r)

Putting the Values,

⇒ 1.1 = 12 / (10 + r)

⇒ 11 + 1.1r = 12

⇒ 1.1r = 1

⇒ r = 1 / 1.1

⇒ r = 10/11 Ω

∴ Internal resistance of battery is 10/11 Ω