Question

A galvanometer of resistance 50 $\Omega$ gives full scale defleciton when a current ${10}^{-3}$ A is passed through it converted into an ammeter to measure 0.5 A current.

• A. 50/499 $\Omega$ in parallel
• B. 9/20 $\Omega$ in parallel
• C. 2/99 $\Omega$ in parallel
• D. 20/99 $\Omega$ in parallel

Answer 1

The correct option is A 50/499 $\Omega$ in parallel

Let resistance connected be x

$=\frac{50\times x}{50+x}=Req$

$\therefore 0.5\times \frac{50x}{50+x}={10}^{-3}\times 50$

= 500x = 500+x

499x=50

$x=\frac{50}{499}\Omega$