A conductor of length 0.5 m carrying a current of 4 A is placed perpendicular to a uniform magnetic field of flux density 0.3 T. What is the magnitude of the force acting on the conductor?

The force on a current-carrying conductor in a magnetic field is given by $F = BIL\sin\theta$. Since the conductor is perpendicular to the field, $\theta = 90°$ and $\sin 90° = 1$. Therefore $F = 0.3 \times 4 \times 0.5 = 0.60\,\text{N}$. Option A results from omitting the current value, while option C doubles the correct answer.