Electromagnetism

Electromagnetism• Describes the magnetic field produced by a current-carrying wire (right-

hand rule or left-hand rule)• Names ways of modifying the intensity of the magnetic field produced

by a current-carrying wire (type of wire, current intensity)• Compares the behaviour of a compass in the magnetic field of a magnet

with the magnetic field created by a current-carrying wire• Describes the magnetic field produced by a solenoid (right-hand rule or

left-hand rule)• Names ways of changing the intensity of the magnetic field produced

by a solenoid (nature of the core, intensity of the current, number of turns)

• Names ways of inducing electrical current in a wire (e.g. movement of a magnet, changing the intensity of a magnetic field)

Electromagnetism

• How do magnets react?• Right hand rule– (straight wire and solenoid)

• Increase magnetic field– (straight wire and solenoid)

• How to generate electricity?

Recap on Magnetism

• Magnetism:– All phenomena caused by magnets

• A magnet is an object that can attract other objects containing iron, cobalt or nickel

Magnetism

• Have you ever noticed?– It doesn’t matter which part of the magnet you

bring to iron, it will always attract to a magnet.

– Why?• Iron is made up of small polarized regions called

domains. Each of these act like a small magnet. When you magnetize the iron, the domains align to be attracted to the magnet. Remember opposites attract

• *** IRON, COBALT, NICKEL

Magnetism

• Attraction and Repulsion– Opposites attract– Like poles repel

Electromagnetism

• Electromagnetism:– All phenomena resulting from the interaction

between electricity and magnetism.

– Right Hand rules:• Live Wire

– Thumb points to the negative terminal– Fingers show the direction of the magnetic field

Electromagnetism

• Right Hand rule – Solenoids (a cylindrical coil of live wire)

• You fingers follow the coil and point towards the negative terminal

• Your thumb indicates the magnetic North

Electromagnetism

• How can you tell what is the negative terminal?– In the circuit drawings the negative terminal will

either be identified with a – Or…– In the following symbol the shorter terminal is the

negative one

Electromagnetism

• You can generate an electrical field by…– Moving a conductor in a magnetic field– Moving a magnet around a conductor

• Magnetic field of a life wire– The thumb points in the direction of conventional

current– The fingers show the direction of the magnetic

lines

• Will the magnetic field be clockwise or counter clock wise

• What are the two poles?