Energy Stored In An Inductor

From NCERT Class 12, Chapter 6 (Electromagnetic Induction), the energy stored in the magnetic field of an inductor carrying current $I$ is $U=\frac{1}{2}L{I}^2$, which represents the work done against the back-emf to establish the current from zero. Substituting the values: $U=\frac{1}{2}\times 0.5\times 4^2=\frac{1}{2}\times 0.5\times 16=4\text{J}$. The option 8 J omits the factor of one-half. The option 2 J uses the current linearly instead of squaring it, or drops another factor. The option 16 J forgets both the inductance and the one-half factor. A plausibility check confirms the units: $\text{H}\times {\text{A}}^2=\text{(Vcdotps/A)}\times {\text{A}}^2=\text{VcdotpAcdotps}=\text{J}$, verifying an energy result. This stored energy is released back to the circuit if the current is interrupted, which is why suddenly breaking an inductive circuit can produce a large voltage spike as the field collapses.