Question

A galvanometer of resistance 70 $\Omega$, is converted to an ammeter by a shunt resistance $r_s$ = 0.03$\Omega$. The value of its resistance will become:

• A. 0.025$\Omega$
• B. 0.022$\Omega$
• C. 0.035$\Omega$
• D. 0.03$\Omega$

Answer 1

Answer: (D)

0.03$\Omega$

Here, $R_g$ = 70 $\Omega$, $r_s$=$0.03\Omega$

$R=\frac{R_g{r}_s}{R_g+r_s}$
$\therefore R=\frac{70\times 0.03}{70+0.03}=0.02998=0.03\Omega$