Question

A voltmeter is connected across a battery of emf 12 V and internal resistance of 10 Ω. If the voltmeter resistance is 230 Ω, what reading will be shown by the voltmeter?

Answer 1

Given: E = 12 volt, r = 10 Ω, R = 230 Ω

To find: Reading shown by voltmeter (V)

Formula: i. I = \(\frac{E}{R+r}\)

ii. V = E – Ir

Calculation:

From formula (i),

I = \(\frac{12}{230+10}=\frac{12}{240}=\frac{1}{20}\) A

From formula (ii),

V= 12 – \(\frac{1}{20}\) × 10 = 12 – 0.5

= 11.5 volt