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:

$250\,Wb$

The correct answer is Option 3: $250\,Wb$

From Faraday's Law:

$\text{Induced emf} = \frac{d\phi}{dt}$

Given current $I = \frac{\text{emf}}{R}$, so:

$\frac{d\phi}{dt} = IR$

Therefore, total change in flux:

$\Delta\phi = \int IR \, dt = R \times (\text{area under I--t graph})$

From the figure, area under the current-time graph = 2.5 (A·s)

So, $\Delta\phi = 100 \times 2.5 = 250 \text{ Wb}$