Notes on Magnetism

 

Magnetic Field Around a Current Carrying Wire

Direction of Magnetic Field

Electromagnet

Electromagnetic Induction

 

When a conductor passes through or is passed by a magnetic field, a current is induces in the conductor. One of the two must move.

This is the principle behind the generation of electricity.

 

Induced Voltage

 

Voltage produced in the conductor by the above.

 

Faraday's Law

 

This is the basic law of electromagnetism. The induced voltage in a conductor is directly proportional to the rate at which the conductor cuts the magnetic lines of force.

 

Relay or Solenoid

An electromechanical switch that opens and closes as shown below.

 

Summary

ð Based on the spin of electrons as they orbit about the atom.

ð Like poles repel, unlike poles attract.

ð Flux lines are invisible lines of force that surround a magnet.

ð The flux lines follow the smallest loop possible.

ð A magnetic field surrounds a wire when current flows through it.

ð You can determine the direction of the flux lines around a wire by grasping the wire with the left hand, with the thumb pointing in the direction of current flow.

        The fingers then point in the direction of the flux lines.

ð Electromagnetic induction occurs when a conductor passes through a magnetic field.

ð Faraday's law:  Induced voltage is directly proportional to the rate at which the conductor cuts the magnetic lines of force.

ð AC and DC generators Convert mechanical energy into electrical energy.

ð A relay is an electromechanical switch.