Question

If an ammeter is to be converted into a voltmeter, then we must connect with the ammeter a

• A. Low resistance in parallel
• B. High resistance in parallel
• C. High resistance in series
• D. Low resistance in series

Answer 1

The correct option is C High resistance in series

We know that, a galvanometer behaves as an ammeter if a low resistance is connected to it in parallel.

To convert a galvanometer into a voltmeter of certain range say $V$, a high resistance $R$ is connected in series with the galvanometer so that current passing through the galvanometer of resistance $G$ becomes equal to its full scale deflection value $\left(I_g\right)$. This is possible only if
$V=I_g(G+R)i.e.R=\frac{V}{I_g}-G$


Hence, if a high resistance is connected in series to an ammeter, it behaves as an voltmeter.