Electric generator: ac and dc

Tutormate > CBSE Syllabus-Class 10th Physics > Electric generator: ac and dc

04 Magnetic

DIRECT CURRENT AND ALTERNATING CURRENT

Direct Current: If the current flows in one direction only, it is called a direct current. It is that current which flows in a circuit with a constant magnitude in the same direction.

 

Alternating current: If the current reverses direction after equal intervals of time, it is called alternating current. It is that current whose magnitude and direction change alternately and regularly with the passage of time.

ELECTRIC GENERATOR

Principle of Electric Generator
The electric generator works on the principle that when a straight conductor is moved in a magnetic field, then current is induced in the conductor.

Types of Electric Generator

Electric generators are of two types:

  1. Alternating Current generator (A.C. generator), and
  2. Direct Current generator (or D.C. generator).

CONSTRUCTION OF AN A.C. GENERATOR

 

A simple A.C. generator consists of a rectangular coil ABCD which can be rotated rapidly between the poles N and S of a strong horseshoetype permanent magnet M. The two ends A and D of the rectangular coils are connected to two circular pieces of copper metal called slip rings  R1 and R2 .As the slip rings  R1 and R2  rotate with the coil, the two fixed pieces of carbon called carbon  brushes, B1  and B2 , keep contact with them.
WORKING OF AN A.C. GENERATOR
  • The rectangular coil ABCD is rotated rapidly through an external force, between the poles N and S of the strong horseshoe-type permanent magnet M.
  • According to Faraday’s law of electromagnetic induction, an emf is induced in the coil ABCD. This induced emf causes current to flow through the coil.
  • The direction of induced current is given by Fleming’s Right Hand Rule. The current so produced can be extracted using the slip ring and brush arrangement and utilized.
  • The alternating current (A.C.) produced in India has a frequency of 50 Hz.

D.C. GENERATOR

In order to obtain direct current (which flows in one direction only), a D.C. generator is used. The working of D.C. generator is similar to that of an A.C. generator. The slip rings of an A.C. generator are replaced by a commutator. So, the A.C. voltage generated id converted to D.C. voltage. Thus, it works as a D.C. generator.

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