Question

Two wires of same length are shaped into a square and a circle. If they carry same
current, ratio of magnetic moment is -
(A) 2:1
(B) TT:2
(C) TT:4
(D) 4: TT​

Answer 1

(B) TT:2

this the correct wrong I don't know ok

Answer 2

Answer:

TT:4

Explanation:

Magnetic moment of a loop is given by p

m

=IA

where, I= current through the loop

A= area of loop

Perimeter of square should be equal to the circumference of circle, since wires have same length.

Therefore, 4a=2πr⇒a=

2

πr

.....(i)

In figure (i), magnetic moment of square loop is given by

p

m

1

=I(A

1

)⇒

⇒p

m

1

=

4

Iπ

2

r

2

[from equation (i)] ....(ii)

In Fig. (ii), magnetic moment of circular loop is given by

p

m

2

=I(A

2

)

p

m

2

=I(πr

2

) ....(iii)

From equations (ii) and (iii), we get

⇒

p

m

2

p

m

1

=

4

π

solution