Question

In an ammeter, 5% of the main current passes through the galvanometer. If resistance of the galvanometer is G, the resistance of ammeter will be :

(1) \(\frac {G}{200}\)

(2) \(\frac {G}{199}\)

(3) 199 G

(4) 200 G

(5) \(\frac {G}{20}\)

Answer 1

Correct option is (5) \(\frac {G}{20}\)

\(I_s S =I_gG\)

\(\frac {95}{100}IS=\frac {5I}{100}G\)

\(S=\frac {G}{19}\)

\(R_A =\frac {SG}{S+G} = \frac{\frac{G^2}{19}}{\frac {20G}{19}}\)

\(R_A =\frac{G}{20}\)