Magnetism

Laws of Magnetism

Magnetic Materials

Forces Between Magnets

Induced Magnetism

Methods of Magnetism

&

Demagnetization

Theory of magnetism

Magnetic fields

Magnetic Properties of

Matter

Magnetic Effects of a Current

Please choose a topicDone By: Siddharth

Arora

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Like poles _________

Unlike poles _______

1) repel; attract2) attract; repel3) explode; melt4) disintegrate; fly to the moon

Question 3

Question 2

Question 1

Instructions:

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Laws of magnetism

Which ones of the poles are North?

1) A,B2) none3) B,C4) B,D

Question 3

Question 2

Question 1

Instructions:

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Laws of magnetism

Instructions:

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Laws of magnetism

Magnetic North is geographical _______

1) South2) East3) Space time continuum 4) Centre of the Universe

Question 3

Question 2

Question 1

Laws of Magnetism• When a bar

magnet is suspended freely it always comes to rest in a north south direction.

Magnetic Poles

• Magnetic South is geographical North.

• Magnetic North is geographical South

Magnetic Poles

• Magnetic poles are located at the side of the magnets.

Magnetic & Non-Magnetic Materials

• Magnetic Materials include:– Iron– Cobalt– Nickel

• The rest are alloys of these metals such as steel.

Forces Between Magnets

• Like Poles Attract

• Unlike Poles Repel

Induced Magnetism

• A magnet attracts a non magnetic material by magnetic induction

Methods Of Magnetization

• Heating and Hammering– Place a steel bar in

the north-south direction and heat

– Hammer it while cooling

A magnet formed by this method is __________

A) Strong

B) Weak

Try This Question

Methods Of Magnetization

• Heating and Hammering– Place a steel bar in

the north-south direction and heat

– Hammer it while cooling

A magnet formed by this method is weak

Methods Of Magnetization

• Heating and Hammering– Place a steel bar in

the north-south direction and heat

– Hammer it while cooling

A magnet formed by this method is weak

Methods of Magnetization

• Magnetization by stroking– Done as shown in

diagram

A magnet formed by this method is __________

A) StrongB) Weak

Try This Question

Methods of Magnetization

• Magnetization by stroking– Done as shown in

diagram

A magnet formed by this method is weak

Methods of Magnetization

• Magnetization by stroking– Done as shown in

diagram

A magnet formed by this method is weak

Methods of Magnetization

• Magnetization using an electric current– A solenoid (a length of copper wire wound into

a long coil) is connected to a battery in series.– A iron bar is then placed inside the solenoid– The polarities depend no the direction of the

flow of the current

A magnet created in this way is ________

A) Strong

B) Weak

Try This Question

Methods of Magnetization

• Magnetization using an electric current– A solenoid (a length of copper wire wound into

a long coil) is connected to a battery in series.– A iron bar is then placed inside the solenoid– The polarities depend no the direction of the

flow of the current

A magnet created in this way is strong

Methods of Magnetization

• Magnetization using an electric current– A solenoid (a length of copper wire wound into

a long coil) is connected to a battery in series.– A iron bar is then placed inside the solenoid– The polarities depend no the direction of the

flow of the current

A magnet created in this way is strong

Demagnetization

• A solenoid (a length of copper wire wound into a long coil) is connected to a battery providing alternating current.

• The magnet is then placed inside the solenoid• It is then removed in an East-West direction

Theory of Magnetism

• Magnetic domains (groups of small atomic magnets) are found in each magnet.

• A magnet is formed when all the domains point in one direction.

Magnetic Fields

• The region around the magnet where its effects can be observed is a magnetic field

Magnetic Fields

• Properties of magnetic fields– Outside the magnet

the lines start from the north pole and end at the south pole

– Inside the magnet they continue from the south pole to the north pole

Magnetic Fields

– The lines never cross each other

– The lines behave as though they are pulled taut

– The lines repel each other

– Lines are close together in a stronger field than a weaker field

Magnetic Fields

– The lines tend to pass through a magnetic substance

Magnetic Properties of Matter

• Soft Magnetic Materials– Easy to magnetize– Easy to

demagnetize– Can be used as

electromagnets– E.g.: Iron

Magnetic Properties of Matter

• Hard Magnetic Materials– Hard to magnetize– Hard to

demagnetize– Can be used as

permanent magnets

– E.g.: Steel

Magnetic Properties of Matter

• Permanent magnets– Magnetism is

retained for a long time

Magnetic Properties of Matter

• Electromagnets– Magnetic events

can only be observed for specific intervals of time

Magnetic Properties of Matter

• The strength of an electromagnet can be increased by:– Passing a larger

current through the solenoid

– Increasing the number of turns of the solenoid

Magnetic Properties of Matter

– Inserting a core of a soft magnetic material

A core of a hard magnetic material cannot be used because____________

A) It takes too long to magnetize and demagnetize

B) Its not cool

Try This Question

Magnetic Properties of Matter

– Inserting a core of a soft magnetic material

A core of a hard magnetic material cannot be used because It takes too long to magnetize and demagnetize

Magnetic Properties of Matter

– Inserting a core of a soft magnetic material

A core of a hard magnetic material cannot be used because It takes too long to magnetize and demagnetize

Magnetic Effect of a Current

• Magnetic effects of current means that a current flowing in a wire produces a magnetic field round it.

• As current increases more lines are formed

Magnetic Effect of a Current

• Maxwell’s Corkscrew rule states that the direction of the magnetic field is the same as the direction in which you would turn an ordinary corkscrew to move it in the direction of the current.

Magnetic Effect of a Current

• This can be interpreted as when current is flowing downwards or away from you, the magnetic field is in the clockwise direction

Magnetic Effect of a Current

• The magnetic field when the wire is in the shape of a flat coil or a solenoid, is shown in the diagram