A moving coil galvanometer has a resistance of 40 Ω. It gives a full scale deflection with a current of 2 mA. How is to be modified to convert it to a voltmeter of 5 V range by connecting some resistance?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 2460 Ω connected in series with galvanometer
To convert the moving coil galvanometer into a voltmeter of a given range, one need to connect a series resistance known as resistance multiplier.
Desired voltage range, $V=I_f×R_{total}$
$⇒R_{total}=\frac{V}{I_f}=\frac{5}{0.002}=2500Ω$
$R_{total}=R_G+R_S$ [$R_G$ = Resistance of galvanometer]
$2500=R_S+40$
$⇒R_S=2460Ω$