Q.

A tightly wound 100 turns coil of radius 10 cm carries a current of 7 A. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as 4π×10-7 SI units)             [2024]
 

1 44 mT  
2 4.4 T  
3 4.4 mT  
4 44 T  

Ans.

(3)

Number of turns in the coil, N=100

Radius of coil, r=10 cm=0.1 m

Current flowing in the coil, I=7 A

As, B=μ0NI2r

B=4π×10-7×100×72×0.1=4×3.14×10-7×100×72×0.1

=43.96×10-4=4.4 mT