In the circuit shown, an ideal cell of emf E is connected in series to a non-ideal ammeter and voltmeter. Reading of the voltmeter is V₀. When a resistance is added in parallel to the voltmeter its reading becomes V₀/10 and the reading of the ammeter becomes 10 times the earlier value. Find V₀ in terms of E.

Question

G1 Physics · Accepted Answer

Image Let initial current be I and voltmeter resistance Rᵥ. V₀ = IRᵥ. After adding the parallel resistor, current is 10I and voltmeter voltage is V₀/10, so the new parallel equivalent is Rᵥ/100. Comparing total series voltage drops before and after gives V₀ = E/2.