ElectrostaticsHard

Question

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

Options

A.
B.
C.
D.

Solution

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

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