Faraday's Law of Electromagnetic Induction

Steps:

• Induced emf magnitude is given by ε = N |dΦ/dt|, where Φ = B ⋅ A (flux through coil area A).
• As coil falls, flux changes due to motion through magnetic field B, so dΦ/dt depends on speed v, B, and N.
• Speed v at magnet depends on drop height h via kinematics (v = √(2gh)).
• Field direction affects emf polarity (Lenz's law) but not |dΦ/dt| magnitude.

Why C is correct:

• Faraday's law shows emf magnitude depends on flux change rate, independent of B direction; reversal flips emf sign but preserves |ε|.

Why the others are wrong:

• A: More turns increases N, multiplying ε proportionally.
• B: Higher h boosts terminal speed, raising |dΦ/dt| and ε.
• D: Stronger B enlarges Φ, increasing |dΦ/dt| and ε.

Final answer: C