Question

A battery supplies 0.9 A current through a 2 Ω resistor and 0.3 A current through a 7 Ω resistor when connected one by one. The internal resistance of the battery is ______.

Options

• 2 Ω

• 1.2 Ω

• 1 Ω

• 0.5 Ω

Answer 1

A battery supplies 0.9 A current through a 2 Ω resistor and 0.3 A current through a 7 Ω resistor when connected one by one. The internal resistance of the battery is 0.5 Ω.

Explanation:

Circuit current

`I = E/(r + R) ⇒ E = I(r + R)`

For 2 Ω, E = 0.9(r + 2)   ...(i)

For 7 Ω, E = 0.3(r + 7)   ...(ii)

From equations (i) & (ii),

0.9(r + 2) = 0.3(r + 7)

r = 0.5 Ω