Question

A tangent galvanometer has a coil with $50turns$ and radius equal to $4cm$. A current of $0.1A$ is passing through it. The plane of the coil is set parallel to the earths magnetic meridian. If the value of the earths horizontal component of the magnetic field is $7\times {10}^{-5}$ tesla and ${\mu }_0=4\pi \times {10}^{-7}Wb{A}^{-}{m}^{-1}$, the defection in the galvanometer needle will be:

• A. ${45}^o$
• B. ${48.3}^o$
• C. ${50.7}^o$
• D. ${52.7}^o$

Answer 1

The correct option is B ${48.3}^o$

For tangent galvanometer

I=2rBμ0ntanθ

∴ tanθ=Iμ0n2rB=0.1×4π×10−7×500.04×7×10−5×2=1.12

or

θ=tan−1(1.12)=48.2o