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Asked in GUJCET 2025 · Peak and instantaneous EMF
Given: the generator's emf vanishes at t = 0.
Idea: a coil turning at angular speed ω in a uniform field gives ε = ε₀ sin(ω t + φ); the condition ε = 0 at t = 0 fixes φ = 0, so ε = ε₀ sin ω t.
Physically the coil starts with its plane perpendicular to the field, where the flux is largest and its rate of change is zero.
The emf is largest when sin ω t = 1, that is ω t = π/2.
So the emf is maximum at t = π/(2ω). (It is back to zero at ω t = π and most negative at ω t = (3π)/2.)
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