Question

A moving coil galvanometer has 100 turns and a resistance of 10ohm. The coil is 5 cm long and 4 cm wide. A potential difference of 100mV produces a full scale deflection ( the coil is turned through `60^@`). The flux density in the gap is `1000G`. The required torque of the controlling spring is
A. 1N m
B. 0.1 Nm
C. `1xx10^-2Nm`
D. `1xx10^-4Nm`

Answer 1

Correct Answer - D
`tau_(n)= n I AB costheta `
`=n (V)/(R ) l b B cos theta`.
`=(100xx100xx10^-3xx5xx10^-2xx4xx10^-2xx1000xx10^-4xxcos 60 )/(10)`
`=1xx10^-4N m`