Question

Let r be the distance of a point on the axis of a bar magnet from its centre. The magnetic field at r is always proportional to
(A) 1/r²
(B) 1/r³
(C) 1/r
(D) not necessarily 1/r³ at all points

Answer 1

Answer:

Magnetic field is inversly proportional to the square of the position vector r.

So option (A) is correct.

Explanation:

since we know the biot savart law for a magnetism which sates that magnetic field is

(i) directly proportional to current flowing in the conductor

(ii) directly proportional to length of the conductor

(iii)directly proportional to angle between length the conductor and position vector.

(iv)inversely proportional to cube of the position vector of the conductor.

$B\alpha \frac{IdL\times r }{r^{3} }$..................(1)

so magnetic field is inversly proportional to the square of the position vector r.

Answer 2

Answer:

Explanation:D