Faraday's law induces sinusoidal voltage in rotating coil

Steps:

• Coil rotates at constant angular speed ω in uniform magnetic field B, so magnetic flux Φ = NBA cos(ωt).
• Induced emf follows Faraday's law: ε = -dΦ/dt.
• Differentiating gives ε = NBAω sin(ωt), a sinusoidal variation.
• Slip rings transmit this alternating voltage without rectification.

Why C is correct:

• C depicts sinusoidal voltage, matching ε = NBAω sin(ωt) from Faraday's law of induction.

Why the others are wrong:

• A shows constant voltage, ignoring flux change with rotation.
• B shows linear (triangular) variation, not matching sinusoidal flux derivative.
• D shows rectified or pulsating waveform, but slip rings provide full AC output.

Final answer: C