A DC generator works on the principle of

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Faraday's law of electromagnetic induction

Explanation: A DC generator is an electromechanical device that converts mechanical energy into electrical energy. It operates on Faraday's Law of Electromagnetic Induction, which states that an electromotive force (EMF) is induced in a conductor whenever it cuts across a magnetic field.

Working Principle: When a coil (armature) is rotated in a stationary magnetic field provided by the field poles, the magnetic flux linkage of the coil changes with time. According to Faraday's law, this change in flux induces an EMF in the coil. For a DC generator, this alternating induced EMF is converted into unidirectional (DC) output using a mechanical commutator and brushes.

Key Formulas: $e = -N \frac{d\phi}{dt}$ — Induced EMF based on rate of change of flux; $E = \frac{\phi Z N P}{60 A}$ — EMF equation for a DC generator

Key Points: Mechanical energy is converted into electrical energy using electromagnetic induction.; The commutator acts as a mechanical rectifier to ensure unidirectional current.; Fleming's Right-Hand Rule determines the direction of the induced current.; The magnitude of the induced EMF depends on the flux density, speed of rotation, and number of conductors.

Advantages: Provides stable DC voltage output; Suitable for high-power industrial applications

Disadvantages: Requires constant maintenance of brushes and commutator; Prone to sparking at the commutator surface

Applications: DC arc welding; Battery charging systems; DC motor drive systems

Additional Info: Lenz's Law (Option A) determines the direction of the induced EMF but is not the principle of energy conversion itself.. Ohm's Law (Option B) relates voltage, current, and resistance in a circuit, not the mechanism of generating electricity.

Answer: C is correct — A DC generator generates electrical energy by electromagnetic induction as defined by Faraday's Law.

Exam Tip: Always remember: Generators use Faraday's law of induction (mechanical to electrical), while Motors use the Lorentz force law (electrical to mechanical).

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