According to Faraday’s laws of electromagnetic induction, an emf is induced in a conductor whenever?

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Cuts magnetic lines of flux

Explanation: Faraday’s Law of Electromagnetic Induction states that an electromotive force (emf) is induced in a conductor whenever the magnetic flux linking the circuit changes with time. For a conductor moving in a magnetic field, this occurs when the conductor cuts across the magnetic flux lines.

Working Principle: When a conductor moves such that it cuts magnetic flux lines, the rate of change of flux linkage ($d\Phi/dt$) becomes non-zero. According to the expression $e = -N(d\Phi/dt)$, this change induces a voltage. If the conductor moves parallel to the magnetic field, it cuts zero lines, resulting in no induced emf.

Key Formulas: $e = -N \frac{d\Phi}{dt}$ — Induced emf as a function of the rate of change of magnetic flux; $e = Blv \sin(	heta)$ — Motional emf in a conductor of length $l$ moving with velocity $v$

Key Points: The change in flux linkage is the fundamental requirement for induction.; Motion parallel to flux lines results in zero induced emf.; The maximum emf is induced when the conductor moves perpendicular to the magnetic field.; Faraday's law is the underlying principle for generators and transformers.

Advantages: Enables conversion of mechanical energy to electrical energy.; Form the basis of efficient power distribution via transformers.

Disadvantages: Eddy currents can cause unwanted heating in magnetic cores.; Hysteresis losses occur in magnetic materials during flux reversals.

Applications: Electrical Generators and Alternators; Transformers and Inductors; Induction Cooktops

Additional Info: Option A is incorrect because moving perpendicular is sufficient, but simply being perpendicular while stationary induces nothing.. Option D is incorrect because parallel motion does not cut flux lines.. The negative sign in Faraday's law represents Lenz's Law, indicating the direction of induced emf opposes the cause.

Answer: C is correct — An emf is induced only when there is a relative motion between the conductor and the magnetic field such that the conductor cuts through the magnetic lines of flux.

Exam Tip: Always remember that 'changing flux' is the key phrase; static placement in a magnetic field, no matter the orientation, will never produce an induced emf in a stationary conductor.

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