A galvanometer of resistance `20 Omega `has current senstivity of `5` div/mA. The instrument has 50 divisions. How will you convert it into voltmeter reading upto 25 volt?

Options

A. join a resistance of 1240 Omega in series
B. join a resistance of 2480 Omega in series
C. join a resistance of 2480 Omega in parallel
D. join a shunt of 20 Omega

Answer

B

Explanation

The current for div i.e. for full scale deflection is 10mA `therefore` High resistance R is given by `R=V/I_g-G=(100)/(10 xx 10^(-3))-100 =10000-100=9900 Omega` We csn also use `R=G(n-1) ` where n =125