Question

The force between two bar magnets whose centers are d metres apart is 4.8N. When the separation is made 2d the force is reduced to

A)4.8N
B)1.2 N
C)0.6 N
D)0.3 N

Answer 1

Answer:

D) 0.3 N

Explanation:

In magnetic dipole ,

F α  1/ r⁴

Thus, When the separation is made 2d the force is reduced to below :-

the new Force (F) will becomes = 4.8 / 2⁴ = 4.8 / 16 = 0.3 N

Hence the answer is Option D) 0.3 N

Answer 2

Answer: B)1.2 N

Explanation: Force acting between the bar magnets F∝ 1/r^2

where r is the separation between the two bar magnets.

Thus if the separation between them is increased by 2 times, the force between them gets reduced by 4 times.

So, the new force becomes

F′= F/4

= 4.8/4

​=1.2 N