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In an A.C. generator, the induced emf is zero at t=0. The induced emf at time t=π/ω is ______.

Asked in GSEB Board July 2018; GSEB Board March 2019 · Peak and instantaneous EMF

Answer: (2) zero

Step-by-step solution

Given: the emf is zero at t=0, so V=Vₘ sin ω t.

Idea: the emf follows the sine of the angle ω t through which the coil has turned.

At t=π/ω: ω t=π.

V=Vₘ sin π=0.

Physically, after half a turn the plane of the coil is again perpendicular to the field: the flux is at its extreme and, for that instant, not changing.

So the induced emf is zero.

Why the other options are wrong

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