magnetism laws of magnetism magnetic materials forces between magnets induced magnetism methods of...
TRANSCRIPT
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:
Click on the correct answer
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
Laws of magnetism
Instructions:
Click on the correct answer
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