JEE Physics 2026 Question with Solution

Given: torque $\tau = 0.016\,\text{N m}$, magnetic field $B = 800\,\text{Gauss}$, and angle $\theta = 30^\circ$.

Find: the value of $\alpha$ in $W = \alpha \times 10^{-3}\,\text{J}$.

Convert the magnetic field into SI units:

Using the torque formula for a magnetic dipole:

So,

The work done in rotating a magnetic dipole from stable position $0^\circ$ to unstable position $180^\circ$ is:

Substituting the values:

Writing this in the required form:

Therefore, the value of $\alpha$ is $64$.

Given: $\tau = 0.016\,\text{N m}$ at $\theta = 30^\circ$ and $B = 800\,\text{Gauss} = 0.08\,\text{T}$.

Find: $\alpha$.

From torque,

Hence,

For rotation from most stable to most unstable position, work done is

Therefore, the value of $\alpha$ is $64$.