Question

Explain the meaning of electromagnetic induction. What type of energy is utilized by an electric generator in generating electricity? Draw a labelled diagram of the construction of an a.c. generator and explain its working. What is the frequency of a.c. power supplied in India?

Hint:

In A.C. generators, the frequency is determined by the speed of the rotation of the armature and the number of poles in the generator.

Answer 1

Electromagnetic Induction:
Electromagnetic induction is the process by which a changing magnetic field induces an electromotive force (emf) in a conductor. This phenomenon was first discovered by Michael Faraday in 1831. According to Faraday's law of induction, the magnitude of the induced emf is directly proportional to the rate of change of magnetic flux. \[ \mathcal{E} = - \frac{d\Phi}{dt} \]
where:
- \(\mathcal{E}\) is the induced emf,
- \(\Phi\) is the magnetic flux.

Energy Utilized by an Electric Generator:
An electric generator converts mechanical energy into electrical energy. The mechanical energy is supplied by various sources such as wind, water (hydroelectric power), steam (thermal power), or other mechanical systems. The mechanical energy is used to rotate the armature of the generator, which moves within a magnetic field to induce an emf.
Construction and Working of an A.C. Generator:
An A.C. generator (alternator) consists of the following main parts:
1. Armature: A coil of wire (usually copper) that rotates in the magnetic field.
2. Magnetic Field: Produced by either a permanent magnet or an electromagnet.
3. Slip Rings: These allow the armature to rotate continuously while maintaining electrical contact.
4. Brushes: These maintain contact with the slip rings and allow current to flow out of the generator.

Working:
In an A.C. generator, the armature coil is rotated within a magnetic field. As the armature coil rotates, the magnetic flux through the coil changes, inducing an electromotive force (emf) according to Faraday's law. The direction of the induced emf alternates as the coil rotates, which is why it is called an alternating current (A.C.). The slip rings and brushes ensure that the current can be drawn from the coil, allowing the generator to supply alternating current.
Frequency of A.C. Power Supplied in India:
In India, the frequency of the alternating current (A.C.) supplied is 50 Hz. This means that the current alternates 50 times per second.
Conclusion:
Electromagnetic induction is the fundamental principle behind the operation of A.C. generators. The energy utilized by these generators is mechanical energy, which is converted into electrical energy. The frequency of A.C. power in India is 50 Hz.