Question

You are given an ammeter, a galvanometer and a voltmeter. From these, the device having maximum resistance is

• A. ammeter
• B. galvanometer
• C. voltmeter
• D. all will have the same resistance

Answer 1

Answer: (C)

Electric circuit diagram of ammeter, galvanometer and voltmeter is shown below,
$(i)$ Ammeter

$\Rightarrow R_{eq\left(A\right)}=\frac{R_s{R}_G}{R_G+R_s}$
$(ii)$ Galvanometer

$\Rightarrow R_{eq\left(G\right)}=R_G$
$(iii)$ Voltmeter

$\Rightarrow R_{eq\left(v\right)}=R_G+R_V$
Hence, the order of resistances
$R_{eq\left(v\right)}>R_{req\left(G\right)}>R_{eq\left(A\right)}$
So, the maximum resistance device is voltmeter.