Question

An ammeter of small resistance and a voltmeter of resistance $R$ are connected in series to an electric cell of negligible internal resistance. Their readings are $A$ and $V$ respectively. If another resistance $R$ is connected in parallel with the voltmeter, then

• A. both A and V increases
• B. both A and V decreases
• C. A decreases but V increases
• D. A increases but V decreases.

Answer 1

Answer: (D)

A increases but V decreases.

In this configuration total resistances of the circuit decreases, so, current in the circuit increases. so, reading of ammeter increases.
As the potential difference across ammeter is increased due to increased current, potential drop across voltmeter decreases.
$V_{ammeter}+V_{voltmeter}=$ EMF of cell
Hence, reading of voltmeter decreases.