A galvanometer whose resistance is 120 Ω gives full scale deflection with a current of 0.05 A so that it can read a maximum current of 10 A. A shunt resistance is added in parallel with it. The resistance of the ammeter so formed is

Question

A galvanometer whose resistance is 120 Ω gives full scale deflection with a current of 0.05 A so that it can read a maximum current of 10 A. A shunt resistance is added in parallel with it. The resistance of the ammeter so formed is (A) 0.06 Ω (B) 0.006 Ω (C) 0.6 Ω (D) 6 Ω

Tardigrade Admin · Accepted Answer

Resistance of shunted ammeter =(G S/G+S) Also (i/ig)=1+(G/S) ⇒ (G S/G+S)=(ig ⋅ G/i) ⇒ (G S/G+S)=(0.05 × 120/10)=0.6 Ω

Q. A galvanometer whose resistance is $120 Ω$ gives full scale deflection with a current of $0.05 A$ so that it can read a maximum current of $10 A$ . A shunt resistance is added in parallel with it. The resistance of the ammeter so formed is

$0.06 Ω$

$0.006 Ω$

$0.6 Ω$

$6 Ω$

Resistance of shunted ammeter $= \frac{GS}{G + S}$
Also $\frac{i}{i _{g}} = 1 + \frac{G}{S}$
$\Rightarrow \frac{GS}{G + S} = \frac{i _{g} \cdot G}{i}$
$\Rightarrow \frac{GS}{G + S} = \frac{0.05 \times 120}{10} = 0.6 Ω$

Q. A galvanometer whose resistance is 120Ω gives full scale deflection with a current of 0.05A so that it can read a maximum current of 10A. A shunt resistance is added in parallel with it. The resistance of the ammeter so formed is

0.06Ω

0.006Ω

0.6Ω

6Ω