JEE Main & Advanced Physics Magnetism Question Bank Self Evaluation Test - Magnetism and Matter

  • question_answer
    Force between two identical bar magnets whose centres are r metre apart is 4.8 N, when their axes are in the same line. If separation is increased to r, the force between them is

    A) 2.4 N

    B) 1.2N

    C) 0.6 N

    D) 0.3 N

    Correct Answer: D

    Solution :

    [d] Force between two short bar magnets is given by \[F\,\,\,\,\,=\,\,\,\,\frac{{{\mu }_{0}}}{4\pi }\frac{6{{M}_{1}}{{M}_{2}}}{{{r}^{4}}}\] \[\therefore \,\,\,\,\,\,\frac{{{F}_{1}}}{{{F}_{2}}}=\frac{r_{2}^{4}}{r_{1}^{4}}={{\left( \frac{2r}{r} \right)}^{4}}\] or  \[{{F}_{2}}=\frac{{{F}_{1}}}{16}=\frac{4.8}{16}=0.3\,N\].


You need to login to perform this action.
You will be redirected in 3 sec spinner