The current i in a coil varies with time as shown in the figure. The variation of induced emf with time would be

Step-by-step solution

Induced emf, e = - L di dt For 0 ≤ t ≤ T 4 , i-t graph is a straight line with positive constant slope. ∴ di dt = constant ⇒ e = - ve and constant For 0 ≤ t ≤ T 4 For T 4 ≤ t ≤ T 2 , ∵ i is constant ∴ di dt = 0 ⇒ e = 0 For T 4 ≤ t ≤ T 2 For T 2 ≤ t ≤ 3 T 4 , i-t graph is a straight line with negative constant slope. ∴ di dt = constant ⇒ e = + ve and constant For T 2 ≤ t ≤ 3 T 4 For 3 T 4 ≤ t ≤ T , i is zero ∴ di dt = 0 ⇒ e = 0 For 3 T 4 ≤ t ≤ T From this analysis, the variation of induced emf with time as shown in