JEE Main · 2017 · 02 Apr 2017 · Offline · Electromagnetic Induction

In a coil of resistance

100 Ω

, a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is:

(A)250 Wb✓ Correct
(B)275 Wb
(C)200 Wb
(D)225 Wb

Answer: (A)

Solution

By Faraday's law the induced emf is

ε = - \frac{d Φ}{d t}

, and in the coil

ε = i R

, so

d Φ = R i d t

. The total change in flux is therefore

R

times the area under the current-time graph. That graph is a right triangle: the current falls linearly from

10 A

0

over

0.5 s

, so the area is

\frac{1}{2} \times 0.5 \times 10 = 2.5 C

. Thus

∣ΔΦ∣ = R \times 2.5 = 100 \times 2.5 = 250 Wb

JEE Main · 2017 · 02 Apr 2017 · Offline · Single correct option

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