Magnetism

1
The font used in this presentation is 1979If
your computer does not have this fontit will
display in Arial Sorry for the inconvenience
caused
Magnetism
Laws of Magnetism
Magnetic fields
Magnetic Materials
Magnetic Properties of Matter
Forces Between Magnets
Magnetic Effects of a Current
Induced Magnetism
Methods of Magnetism Demagnetization
Theory of magnetism
Please choose a topic
Done By Siddharth Arora
2
Laws of magnetism
Like poles _________ Unlike poles _______ 1)
repel attract2) attract repel3) explode
melt4) disintegrate fly to the moon
Question 3 Question 2 Question 1
Instructions Click on the correct answer
3
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 Click on the correct answer
4
Laws of magnetism
Magnetic North is geographical _______ 1)
South2) East3) Space time continuum 4)
Centre of the Universe
Question 3 Question 2 Question 1
Instructions Click on the correct answer
5
Sorry! Wrong answer
Click here to try again
6
Laws of Magnetism

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

7
Magnetic Poles

• Magnetic South is geographical North.
• Magnetic North is geographical South

8
Magnetic Poles

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

9
Magnetic Non-Magnetic Materials

• Magnetic Materials include
• Iron
• Cobalt
• Nickel
• The rest are alloys of these metals such as steel.

10
Forces Between Magnets

• Like Poles Attract
• Unlike Poles Repel

11
Induced Magnetism

• A magnet attracts a non magnetic material by
  magnetic induction

12
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 __________
• Strong
• Weak

Try This Question
13
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
14
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
15
Methods of Magnetization

• Magnetization by stroking
• Done as shown in diagram

A magnet formed by this method is __________ A)
Strong B) Weak
Try This Question
16
Methods of Magnetization

• Magnetization by stroking
• Done as shown in diagram

A magnet formed by this method is weak
17
Methods of Magnetization

• Magnetization by stroking
• Done as shown in diagram

A magnet formed by this method is weak
18
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
• Weak

Try This Question
19
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
20
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
21
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

22
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.

23
Magnetic Fields

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

24
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

25
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

26
Magnetic Fields

• The lines tend to pass through a magnetic
  substance

27
Magnetic Properties of Matter

• Soft Magnetic Materials
• Easy to magnetize
• Easy to demagnetize
• Can be used as electromagnets
• E.g. Iron

28
Magnetic Properties of Matter

• Hard Magnetic Materials
• Hard to magnetize
• Hard to demagnetize
• Can be used as permanent magnets
• E.g. Steel

29
Magnetic Properties of Matter

• Permanent magnets
• Magnetism is retained for a long time

30
Magnetic Properties of Matter

• Electromagnets
• Magnetic events can only be observed for specific
  intervals of time

31
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

32
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
33
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
34
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
35
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

36
Magnetic Effect of a Current

• Maxwells 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.

37
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

38
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