Magnetism PPT Physics Class 12

 Page 1


MAGNETISM
1. Bar Magnet and its properties
2. Current Loop as a Magnetic Dipole and Dipole Moment
3. Current Solenoid equivalent to Bar Magnet
4. Bar Magnet and it Dipole Moment
5. Coulomb’s Law in Magnetism
6. Important Terms in Magnetism
7. Magnetic Field due to a Magnetic Dipole
8. Torque and Work Done on a Magnetic Dipole
9. Terrestrial Magnetism
10.Elements of Earth’s Magnetic Field
11.Tangent Law
12.Properties of Dia-, Para- and Ferro-magnetic substances
13.Curie’s Law in Magnetism
14.Hysteresis in Magnetism
Page 2


MAGNETISM
1. Bar Magnet and its properties
2. Current Loop as a Magnetic Dipole and Dipole Moment
3. Current Solenoid equivalent to Bar Magnet
4. Bar Magnet and it Dipole Moment
5. Coulomb’s Law in Magnetism
6. Important Terms in Magnetism
7. Magnetic Field due to a Magnetic Dipole
8. Torque and Work Done on a Magnetic Dipole
9. Terrestrial Magnetism
10.Elements of Earth’s Magnetic Field
11.Tangent Law
12.Properties of Dia-, Para- and Ferro-magnetic substances
13.Curie’s Law in Magnetism
14.Hysteresis in Magnetism
Magnetism:
- Phenomenon of attracting magnetic substances like iron, nickel, cobalt, etc.
• A body possessing the property of magnetism is called a magnet.
• A magnetic pole is a point near the end of the magnet where magnetism is 
concentrated.
• Earth is a natural magnet.
•The region around a magnet in which it exerts forces on other magnets and 
on objects made of iron is a magnetic field.
Properties of a bar magnet:
1. A freely suspended magnet aligns itself along North – South direction.
2. Unlike poles attract and like poles repel each other.
3. Magnetic poles always exist in pairs. i.e. Poles can not be separated.
4. A magnet can induce magnetism in other magnetic substances.
5. It attracts magnetic substances.
Repulsion is the surest test of magnetisation: A magnet attracts iron rod as well 
as opposite pole of other magnet.  Therefore it is not a sure test of magnetisation.
But, if a rod is repelled with strong force by a magnet, then the rod is surely 
magnetised.
Page 3


MAGNETISM
1. Bar Magnet and its properties
2. Current Loop as a Magnetic Dipole and Dipole Moment
3. Current Solenoid equivalent to Bar Magnet
4. Bar Magnet and it Dipole Moment
5. Coulomb’s Law in Magnetism
6. Important Terms in Magnetism
7. Magnetic Field due to a Magnetic Dipole
8. Torque and Work Done on a Magnetic Dipole
9. Terrestrial Magnetism
10.Elements of Earth’s Magnetic Field
11.Tangent Law
12.Properties of Dia-, Para- and Ferro-magnetic substances
13.Curie’s Law in Magnetism
14.Hysteresis in Magnetism
Magnetism:
- Phenomenon of attracting magnetic substances like iron, nickel, cobalt, etc.
• A body possessing the property of magnetism is called a magnet.
• A magnetic pole is a point near the end of the magnet where magnetism is 
concentrated.
• Earth is a natural magnet.
•The region around a magnet in which it exerts forces on other magnets and 
on objects made of iron is a magnetic field.
Properties of a bar magnet:
1. A freely suspended magnet aligns itself along North – South direction.
2. Unlike poles attract and like poles repel each other.
3. Magnetic poles always exist in pairs. i.e. Poles can not be separated.
4. A magnet can induce magnetism in other magnetic substances.
5. It attracts magnetic substances.
Repulsion is the surest test of magnetisation: A magnet attracts iron rod as well 
as opposite pole of other magnet.  Therefore it is not a sure test of magnetisation.
But, if a rod is repelled with strong force by a magnet, then the rod is surely 
magnetised.
Representation of Uniform Magnetic Field:
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
Uniform field on the 
plane of the diagram
Uniform field 
perpendicular & into the 
plane of the diagram
Uniform field perpendicular 
& emerging out of the plane 
of the diagram
Current Loop as a Magnetic Dipole & Dipole Moment:
I
B
Magnetic Dipole Moment is
M = I A  n
SI unit is A m
2
.
A
TIP:
When we look at any one side of the loop carrying current, if the current 
is in anti-clockwise direction then that side of the loop behaves like 
Magnetic North Pole and if the current is in clockwise direction then 
that side of the loop behaves like Magnetic South Pole.
Page 4


MAGNETISM
1. Bar Magnet and its properties
2. Current Loop as a Magnetic Dipole and Dipole Moment
3. Current Solenoid equivalent to Bar Magnet
4. Bar Magnet and it Dipole Moment
5. Coulomb’s Law in Magnetism
6. Important Terms in Magnetism
7. Magnetic Field due to a Magnetic Dipole
8. Torque and Work Done on a Magnetic Dipole
9. Terrestrial Magnetism
10.Elements of Earth’s Magnetic Field
11.Tangent Law
12.Properties of Dia-, Para- and Ferro-magnetic substances
13.Curie’s Law in Magnetism
14.Hysteresis in Magnetism
Magnetism:
- Phenomenon of attracting magnetic substances like iron, nickel, cobalt, etc.
• A body possessing the property of magnetism is called a magnet.
• A magnetic pole is a point near the end of the magnet where magnetism is 
concentrated.
• Earth is a natural magnet.
•The region around a magnet in which it exerts forces on other magnets and 
on objects made of iron is a magnetic field.
Properties of a bar magnet:
1. A freely suspended magnet aligns itself along North – South direction.
2. Unlike poles attract and like poles repel each other.
3. Magnetic poles always exist in pairs. i.e. Poles can not be separated.
4. A magnet can induce magnetism in other magnetic substances.
5. It attracts magnetic substances.
Repulsion is the surest test of magnetisation: A magnet attracts iron rod as well 
as opposite pole of other magnet.  Therefore it is not a sure test of magnetisation.
But, if a rod is repelled with strong force by a magnet, then the rod is surely 
magnetised.
Representation of Uniform Magnetic Field:
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
Uniform field on the 
plane of the diagram
Uniform field 
perpendicular & into the 
plane of the diagram
Uniform field perpendicular 
& emerging out of the plane 
of the diagram
Current Loop as a Magnetic Dipole & Dipole Moment:
I
B
Magnetic Dipole Moment is
M = I A  n
SI unit is A m
2
.
A
TIP:
When we look at any one side of the loop carrying current, if the current 
is in anti-clockwise direction then that side of the loop behaves like 
Magnetic North Pole and if the current is in clockwise direction then 
that side of the loop behaves like Magnetic South Pole.
B
I
I
x x x x x x x
B
Current Solenoid as a Magnetic Dipole or Bar Magnet:
TIP: Play previous and next to understand the similarity of field lines.
Page 5


MAGNETISM
1. Bar Magnet and its properties
2. Current Loop as a Magnetic Dipole and Dipole Moment
3. Current Solenoid equivalent to Bar Magnet
4. Bar Magnet and it Dipole Moment
5. Coulomb’s Law in Magnetism
6. Important Terms in Magnetism
7. Magnetic Field due to a Magnetic Dipole
8. Torque and Work Done on a Magnetic Dipole
9. Terrestrial Magnetism
10.Elements of Earth’s Magnetic Field
11.Tangent Law
12.Properties of Dia-, Para- and Ferro-magnetic substances
13.Curie’s Law in Magnetism
14.Hysteresis in Magnetism
Magnetism:
- Phenomenon of attracting magnetic substances like iron, nickel, cobalt, etc.
• A body possessing the property of magnetism is called a magnet.
• A magnetic pole is a point near the end of the magnet where magnetism is 
concentrated.
• Earth is a natural magnet.
•The region around a magnet in which it exerts forces on other magnets and 
on objects made of iron is a magnetic field.
Properties of a bar magnet:
1. A freely suspended magnet aligns itself along North – South direction.
2. Unlike poles attract and like poles repel each other.
3. Magnetic poles always exist in pairs. i.e. Poles can not be separated.
4. A magnet can induce magnetism in other magnetic substances.
5. It attracts magnetic substances.
Repulsion is the surest test of magnetisation: A magnet attracts iron rod as well 
as opposite pole of other magnet.  Therefore it is not a sure test of magnetisation.
But, if a rod is repelled with strong force by a magnet, then the rod is surely 
magnetised.
Representation of Uniform Magnetic Field:
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
x     x     x      x      x 
Uniform field on the 
plane of the diagram
Uniform field 
perpendicular & into the 
plane of the diagram
Uniform field perpendicular 
& emerging out of the plane 
of the diagram
Current Loop as a Magnetic Dipole & Dipole Moment:
I
B
Magnetic Dipole Moment is
M = I A  n
SI unit is A m
2
.
A
TIP:
When we look at any one side of the loop carrying current, if the current 
is in anti-clockwise direction then that side of the loop behaves like 
Magnetic North Pole and if the current is in clockwise direction then 
that side of the loop behaves like Magnetic South Pole.
B
I
I
x x x x x x x
B
Current Solenoid as a Magnetic Dipole or Bar Magnet:
TIP: Play previous and next to understand the similarity of field lines.
Bar Magnet:
S
N
P P
Magnetic Length
Geographic  Length
M
1. The line joining the poles of the magnet        
is  called magnetic axis.
2.  The distance between the poles of the 
magnet is called magnetic length of the 
magnet.
Magnetic Dipole & Dipole Moment:
A pair of magnetic poles of equal and opposite strengths separated by a 
finite distance is called a magnetic dipole.
The magnitude of dipole moment is the product of the pole strength m and 
the separation 2l between the poles.
3. The distance between the ends of the magnet is called the geometrical 
length of the magnet.
4. The ratio of magnetic length and geometrical length is nearly 0.84.
Magnetic Dipole Moment is         M = m.2l. l
The direction of the dipole moment is from South pole to North Pole
along the axis of the magnet.          
SI unit of pole strength is A.m