A galvanometer coil has a resistance of 10 Ω and the ammeter shows full scale deflection for a current of 1 mA. The shunt resistance required to convert the galvanometer into an ammeter of range 0-100 mA is about

Question

A galvanometer coil has a resistance of 10 Ω and the ammeter shows full scale deflection for a current of 1 mA. The shunt resistance required to convert the galvanometer into an ammeter of range 0-100 mA is about (A) 10 Ω  (B) 1 Ω  (C) 0.1 Ω  (D) 12.48 Ω

Tardigrade Admin · Accepted Answer

Let shunt resistance be S Voltage across shunt is Now, V=(I-Ig) .S and Ig ⋅ RG=(I-Ig) .S ⇒ S=(Ig RG/(I-Ig)) =(10-3 × 10/(100 × 10-3-1 × 10-3)) =(10/99)=0.1 Ω

Q. A galvanometer coil has a resistance of $10 Ω$ and the ammeter shows full scale deflection for a current of $1 m A$ . The shunt resistance required to convert the galvanometer into an ammeter of range $0 - 100 m A$ is about

$10 Ω$

$1 Ω$

$0.1 Ω$

$12.48 Ω$

Let shunt resistance be $S$
Voltage across shunt is
Now, $V = (I - I_{g}) . S$
and $I_{g} \cdot R_{G} = (I - I_{g}) . S$
$\Rightarrow S = \frac{I _{g} R _{G}}{( I - I _{g} )}$
$= \frac{1 0 ^{- 3} \times 10}{( 100 \times 1 0 ^{- 3} - 1 \times 1 0 ^{- 3} )}$
$= \frac{10}{99} = 0.1 Ω$

Q. A galvanometer coil has a resistance of 10Ω and the ammeter shows full scale deflection for a current of 1mA. The shunt resistance required to convert the galvanometer into an ammeter of range 0−100mA is about

10Ω

1Ω

0.1Ω

12.48Ω