JEE Main 2024 Physics question
A rectangular loop of sides 12 cm and 5 cm, with its sides parallel to the x-axis and y-axis respectively, moves with a velocity of 5 cm/s in the positive x-axis direction, in a space containing a variable magnetic field in the positive z direction. The field has a gradient of T/cm along the negative x direction and it is decreasing with time at the rate of T/s. If the resistance of the loop is 6 mΩ, the power dissipated by the loop as heat is × W.
Answer: 216
Solution
dB/dt seen by the loop = 1 × 10⁻³ + (0.1 T/m)(0.05 m/s) = 6 × 10⁻³ T/s; emf = 6 × 10⁻³ × 6 × 10⁻³ = 3.6 × 10⁻⁵ V; P = emf²/R = 216 × 10⁻⁹ W.