Assertion : When radius of a circular loop carrying current is doubled, its magnetic moment becomes four…
Assertion : When radius of a circular loop carrying current is doubled, its magnetic moment becomes four times.
Reason : Magnetic moment depends on area of the loop.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Solution
Magnetic dipole moment of the current loop
$=$ Ampere turns $\times$ Area of the coil or $M=N I \pi r^2$
When radius of the coil becomes double, new magnetic moment will be
$M_1=N I \pi(2 r)^2=4 N I \pi r^2=4 M$
Hence magnetic moment becomes four times when radius is doubled.