EET 208 Electrical Power Technology By Mohd Saufi

EET 208 Electrical Power Technology By Mohd Saufi Ahmad Chapter 2 Electromagnetism

Electromagnetism is the branch of science concerned with the forces that occur between electrically charge particles. In electromagnetic theory these forces are explained using electromagnetic field.

Magnetic Field �The pointer of compass is called a permanent magnet because it always retains its peculiar properties if it suspended in a horizontal plane. �In permanent magnet, it is called North Pole (or N) and the other end is called the South Pole (or S).

Magnetic Field �Place a permanent magnet on a table, cover it over with a sheet of smooth cardboard and sprinkle steel filings to the cardboard. �The shape and density of these chains enable one to form a mental picture of the magnetic condition of space or field around a bar magnet. Its called magnetic

Direction of Magnetic Field �The lines of magnetic flux are assumed to pass through the magnet, emerge from the N pole and return to the S pole

Magnetic field due to an electrical current �If the current is flowing away from us, the magnetic field has a clockwise direction and the lines of magnetic flux can be represented by concentric circles around the wire. �A method of representing the relationship between the direction of a current and magnetic flux is right

Force on Current-Carrying Conductor �The mechanical force exerted by the conductor always act in a direction perpendicular to the plane of the conductor and magnetic field direction. �The direction is given the left-hand rule.

Force on Current-Carrying Conductor

Electromagnetic Induction � Electromagnetic induction is the production of an electric current across a conductor moving through a magnetic field. � This situation called induction because there is no physical connection between the conductor and the magnet. The current is said to be induced in the conductor by the magnetic field.

Faraday’s Law �Faraday’s law of induction is a basic law of electromagnetism that predicts how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF). It is the fundamental operating principle of transformers, inductors, and many types of electrical motors and generators.

Faraday’s Law

Direction of induced e. m. f Lenz’s Law The direction of an induced e. m. f is always such that it tends to set up a current opposing the motion or the change of flux responsible for inducing that e. m. f

Induced e. m. f

Direction of Induced e. m. f Fleming’s right-hand rule If the index finger of the right hand is pointed in the direction of the magnetic flux, thumb is pointed in the direction of motion of the conductor relative to the magnetic field, the middle finger represents the direction of the e. m. f

Induced voltage on a conductor moving in a magnetic field

Question 1

Question 2

Question 3

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