Do Now

Write a few sentences to describe the characteristics of magnets that you know?

There are no individual magnetic poles

(or magnetic charges). Electric charges can

be separated, but magnetic poles always

come in pairs - one north and one

south. Opposite poles (N and

S) attract and like poles (N and N,

or S and S) repel.

Magnetic fieldA magnetic field is the region around themagnet that has the magnetic force. A magneticfield is strongest at the poles.

What is magnetism?Magnetism is the properties and interactions of magnetsMagnets produce magnetic forces and have magnetic field lines

Unlike poles of magnets attract each other and like poles of magnets repel.

How to draw magnet field lines• Outside the magnet lines of force are directed from the

north pole towards the south pole of the magnet.• But within the magnet the magnetic lines are directed from

the south pole towards the north pole.• Lines of force repel each other.• Lines of force never intersect.

When you draw a magnetic field, draw the curve lines from north pole to south pole and closest together at the poles.

N S

S N N S

N S S N

Which diagram best represents a magnetic field between two magnetic poles?

The earth is like a giant magnet!The nickel iron core of the earth gives the earth a magnetic field much like a bar magnet.

Earth's magnetic field

The Earth's magnetic field appears to come from a giant bar

magnet, but with its south pole located

up near the Earth's north pole

(near Canada).The magnetic field lines come out of the Earth

near Antarctica and enter near Canada.

CompassA compass is a magnet. The south pole of the

compass is attracted to (points to) the north pole of a magnet.

Do Now1. Which diagram best represents the position of the

needle of the compass as it responds to the magnetic field of the bar magnet?

2. Write a few sentences to explain your answer.

Electricity and Magnetism – how are they related?

When an electric current passes through a wire a magnetic field is formed.

What is an electromagnet?When an electric current is passed through a coil of wire wrapped around a metal core, a very strong magnetic field is produced. This is called an electromagnet.

Electricity and Magnetism – how are they related?

Moving a loop of wire through a magnetic field produces an electric current. This is electromagnetic induction.

Electromagnetic InductionIf a wire (conductor) “cuts” across the magneticfield lines then a potential difference will beproduced in the wire. The difference in potential

created in a conductor due to its relative motion in a magnetic field is called an induced potential difference.

Motion of

conductor

North South

Induced potential differenceThe amount of potential difference produced depends on• The length of the conductor, • The strength of the magnetic field, • The speed at which the conductor passes through the field• The angular direction at which the conductor passes

through the field.

x x x x magnetic x x x x field x x x x directed x x x x into the page

Do Now

1.The diagram below represents a wire conductor, RS, positioned perpendicular to a uniform magnetic field directed goes into the page. Describe the direction in which the wire could be moved to produce the maximum potential difference across its ends, R and S.

R x x x x magnetic x x x x field x x x x directed x x x x into the page

S

An electron traveling at a speed (v) in the plane of this paper enters a uniform magnetic field. Which diagram best represents the condition under which the electron will experience the greatest magnetic force as it enters the magnetic field?

A generator is used to convert mechanical energy into electrical energy by electromagnetic induction.

What are electric motors?An electric motor is a device which changes electrical energy into mechanical energy.

Go to the next slide

How does an electric motor work?

Simple as that!!

The generator works on the principle of electromagnetic induction - the flow of electric charges could be induced by moving an electrical conductor, such as a wire in a magnetic field.

What is a magnetThe earliest magnets were found naturally in the mineral

magnetite which is abundant the rock-type lodestone. These magnets were used by the ancient peoples as compasses to guide sailing vessels.

A magnet attracts iron and has two ends, northpole and south pole.

Which diagram best represents the magnetic field near the poles of a horseshoe magnet?

What are magnetic domains?Magnetic substances like iron, cobalt, and nickel are composed of small areas where the groups of atoms are aligned like the poles of a magnet. These regions are called domains. All of the domains of a magnetic substance tend to align themselves in the same direction when placed in a magnetic field. These domains are typically composed of billions of atoms.