Question

The coil of a galvanometer is `0.02xx0.8 m^2`. It consists of 200 turns of the wire and is in a magnetic field of 0.20 T. The restoring torque constant of suspension fibre is `10^(-5) Nm//degree.` Assuming magnetic field to be radial
(a) What is the maximum current that can be measured by this galvanometer if scale can accommodate `45^@` deflection?
(b) What is the smallest current that can be detected if minimum observed deflection is `0.1^@`?

Answer 1

We know that `I=C/(NBA) theta`
(a) `I=(10^-5xx45^@)/(200xx0.20xx0.02xx0.8)=7.03xx10^-4A`
(b) `I_(min)=C/(NBA) theta_(min)`
`=(10^-5xx0.1^@)/(200xx0.20xx0.02xx0.8)=1.56xx10^-6A`