A galvenometer with a coil of resistance `12.0 Omega` shows full-scale deflection for a current of `2.5 mA`. How will you convert the meter into
(a) an ammoter of range `0` to `7.5 A`?
(b) a voltmeter of range `0` to `1.0 V`?

Explanation

Given , `G = 12.0 Omega`, `I_(g) = 2.5 mA = 2.5 xx 10^(-3) A`
(i) `I = 7.5 A, S = ?`
`S = G xx (I_(g))/(I - I_(g)) = 12 xx (2.5 xx 10^(-3))/(7.5 - 2.5 xx 10^(-3)) Omega ~~ 4.0 xx 10^(-3) Omega`
(ii) `V = 0.1 V,R = ?`
`:. R = (V)/(I_(g)) -G = (0.1)/(2.5 xx 10^(-3)) - 12.0 = 388 Omega`