Question

A galvanometer may be converted into an ammeter or voltmeter. In which of the following cases the resistance of the device will be the largest ?
$($Assume maximum current range of galvanometer $=1\text{mA})$

• A. an ammeter of range $10\text{A}$
• B. a voltmeter of range $5\text{V}$
• C. an ammeter of range $5\text{A}$
• D. a voltmeter of range $10\text{V}$

Answer 1

The correct option is D a voltmeter of range $10\text{V}$

The greater the resistance of the voltmeter, more accurate will be its reading. Ideal voltmeter has infinite resistance.

Good ammeter has very small resistance compared to other resistors in the circuit. Ideal ammeter has almost zero resistance.

According to question , we want a device with the largest resistance, hence we will choose voltmeter. Also, a high range voltmeter has higher resistance.
Thus, option (d) is the correct answer.