Question

# A circular coil of radius 5 cm carries an electric current I and magnetic field at the centre is B. The magnetic field due to the coil at a point 5 m from the centre on the axis will be -

A
B106
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
B
B104
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
B102
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
B10
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

## The correct option is A B106 The magnetic field at the centre (O) of the loop is, BO=B=μ0I2R ....(1) The magnetic field at a point P on the axis of loop at a distance r from the centre is, BP=μ04π×2πIR2(R2+r2)3/2 For the given problem, ∵R(=5 cm)<<r(=5 m)⇒R2+r2≈r2 ∴BP=μ04π×2πIR2r3=μ0IR22r3 ....(2) On dividing equation (1) by (2), we get, BOBP=μ0I2Rμ0IR22r3=r3R3=(rR)3 ⇒BOBP=(55×10−2)3=106 ⇒BP=BO106=B106 Hence, option (A) is the correct answer.

Suggest Corrections
0
Related Videos
PHYSICS
Watch in App
Explore more