A galvanometer of resistance `100Omega` has 50 divisions on its scale and has sensitivity of `20 mu`A/ division. It is to be converted to a voltmeter with three ranges, of `0-2V, 0-10V and 0-20V`. The appropriate circuit to do so is:

Options

A.
B.
C.
D.

Answer

c

Explanation

Current for full scale deflection ` = 20 xx 10^(-6) xx 50 = 10^(-3)` Amp
We can now use V = IR for the three ranges as follows:
` 2 = 10^(-3) xx (100 + R_(1)) rArr R_(1) = 1900 Omega`
`10 = 10^(-3) xx (2000 + R_(2)) rArr R_(2) = 8000 Omega`
` 20 = 10^(-3) xx (1000 + R_(3)) rArr R_(3) = 10000 Omega`
We can see that option (c ) is corrent .