Assertion : If the current in a solenoid is r | vedclass

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(C) The magnetic field $B$ inside a solenoid is given by $B = \mu_0 n I$,where $I$ is the current.The magnetic field energy density $u$ is given by $u

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If Assertion is correct but Reason is incorrect.

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(C) The magnetic field $B$ inside a solenoid is given by $B = \mu_0 n I$,where $I$ is the current.The magnetic field energy density $u$ is given by $u = \frac{B^2}{2\mu_0} = \frac{(\mu_0 n I)^2}{2\mu_0} = \frac{1}{2} \mu_0 n^2 I^2$.Since the energy density $u$ is proportional to $I^2$,reversing the direction of the current (i.e.,changing $I$ to $-I$) does not change the value of $I^2$.Therefore,the magnetic field energy stored in the solenoid remains constant.Since the Assertion claims the energy decreases,the Assertion is incorrect.The Reason states that energy density is proportional to the square of the current,which is correct.Thus,the Assertion is incorrect and the Reason is correct.

Assertion : If the current in a solenoid is reversed in direction while keeping the same magnitude,the magnetic field energy stored in the solenoid decreases.
Reason : Magnetic field energy density is proportional to the square of the current.

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Assertion : If the current in a solenoid is reversed in direction while keeping the same magnitude,the magnetic field energy stored in the solenoid decreases.Reason : Magnetic field energy density is proportional to the square of the current.