A cell of emf and internal resistance is connected in series with a variable resistor
PHYSICS · Multi-part · CBSE · Physics · Current Electricity · Current Electricity
Problem
A cell of emf 2.0V and internal resistance 0.50Ω is connected in series with a variable resistor R. A voltmeter of resistance 1000Ω is permanently connected directly across the terminals of the cell.
(i) When R is kept open (no external load), what reading will the voltmeter show? Explain your reasoning briefly.
(ii) The resistor R is now set to 4.5Ω and connected in the circuit. Calculate (a) the current in the circuit and (b) the voltmeter reading in this condition.
(iii) Explain qualitatively why the reading obtained in part (ii) is smaller than that obtained in part (i) although the emf of the cell remains unchanged.