Question

Force between two identical short bar magnets whose centers are r meter apart is 4.8 N when their axes are in the same line. If the separation is increased to 2 r meter, the force between them is reduced to

• A. $0.3N$
• B. $0.6N$
• C. $2.4N$
• D. $1.2N$

Answer 1

The correct option is A $0.3N$

$\text{Solution}$:

We know in magnetic dipole,

force $\propto \frac{1}{r^4}$

Hence, new force=$\frac{4.8}{2^4}$

=$\frac{4.8}{16}$

= 0.3N

$\text{Hence A is the correct option}$

∝1r4