JEE Main · 2024 · 29 Jan 2024 · Shift 1 · Current Electricity

A galvanometer having coil resistance

10Ω

shows a full scale deflection for a current of 3 mA. For it to measure a current of 8 A, the value of the shunt should be:

Answer: (C)

Solution

Galvanometer resistance

G = 10 Ω

, full-scale current

I_{g} = 3 mA

, required range

I = 8 A

.

For a shunt

S

in an ammeter conversion,

I_{g} G = (I - I_{g}) S

S = \frac{I _{g} G}{I - I _{g}} = \frac{( 3 \times 1 0 ^{- 3} ) ( 10 )}{8 - 0.003} = \frac{0.03}{7.997} \approx 3.75 \times 1 0^{- 3} Ω

Key confirmed: C.

JEE Main · 2024 · 29 Jan 2024 · Shift 1 · Single correct option