Question

# A coil carrying current 'I' has radius 'r' and number of turns 'n'. It is rewound so that radius of new coil is 'r4' and it carries current 'I'. The ratio of magnetic moment of new coil to that of original coil is

A
1
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
12
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
14
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
D
18
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

## The correct option is C 14Initially, the radius of the coil r1=rArea of the coil initially A=πr2=πr2Thus initial magnetic moment of the coil μ1=nIA=2πnIr2Now the coil is rewound to form a new coil of radius r=r4 having n′ turns. Length of the coil before and after its is rewounded remains the same.∴ n(2πr)=n′(2π×r4)⟹ n′=4nArea of the new coil A′=π(r′)2=πr216Magnetic moment of new coil μ′=n′IA′∴ μ′=(4n)I×πr216=πnIr24Thus ratio of magnetic moments μ′μ=πnr2/4πnr2⟹ μ′μ=14

Suggest Corrections
0
Related Videos
Torque on a Magnetic Dipole
PHYSICS
Watch in App
Explore more