Introduction of MAGNETIC EFFECT OF CURRENT

1. Priyanka Jakhar
Physics Lecturer
GGIC Vijay Nagar
Ghaziabad U.P.
Class 12th Physics
Introduction of
MAGNETIC EFFECT OF CURRENT

2. 1. Introduction
2. Magnets and its properties
3. Magnetic Effect of Current – Oersted’s Experiment
4. Ampere’s Swimming Rule
5. Maxwell’s Cork Screw Rule
6. Right Hand Thumb Rule

3. INTRODUCTION
In our childhood, we all might have experienced iron nails getting attracted to a magnet. We have
also witnessed or heard current carrying copper wire wound around iron acting as a magnet in a
science project. That time all of that seemed magical, although it is all science. It is due to
magnetism.
Magnetism is a phenomenon due to which moving charges (or magnets) attract ferromagnetic
objects and repel diamagnetic objects.
This diagram below shows that when iron nails are brought closer to a magnet, they get attracted
and stick to the magnet
History of magnets
•As early as 600 BC in Greece, shepherds observed that their wooden shoes which had iron nails
struck at some places on the ground.
•An island in Greece called magnesia has magnetic ore deposits. The word magnet is derived from
here.
•The technological use of magnet at around 400 BC by Chinese was remarkable. A thin piece of
magnet when suspended freely always points towards North-South direction. This fact was utilised
by a Chinese emperor Huang-ti to win a war.

4. Natural Magnets
A natural magnet is an ore of iron that attracts small pieces of iron, cobalt, and nickel towards it. It
is usually an oxide of iron named Fe3O4.
A natural magnet is a magnet that occurs naturally in nature.
All natural magnets are permanent magnets, meaning they will never lose their magnetic power.
Natural magnets can be found in sandy deposits in various parts of the world.
The strongest natural magnet material is lodestone, also called magnetite.
This mineral is black in color and very shiny when polished. The lodestone was actually used in
the very first compasses ever made.
Examples :-- Magnetite or lodestone is a natural magnet.
Artificial Magnets
A magnet that is prepared artificially form the artificial magnets.
When magnets are made by people, they are called artificial magnets. These magnets are on
your refrigerator door, and they have extra-strong magnetic power, like those really tiny super-
strong magnets that you can buy from toy or science stores.
There are two types of artificial magnets: temporary and permanent.
Temporary magnets:-- become magnetized in the presence of a magnetic field. They lose
their magnetism gradually, when the magnetic field is removed.
Permanent magnets:-- are those magnets whose magnetic strength never fades.
Examples :-- include an electromagnet, a magnetic needle, horseshoe and bar magnets etc.

5. Natural Magnet Artificial Magnet
Horseshoe
Magnet
Magnetic
Needle
Bar Magnet Ring
Magnet
Disc
Magnet

6. MAGNETIC FIELD: Magnetic field is an effect around a permanent magnet or
a moving charge due to which ferromagnetic objects like some metals get
attracted, and diamagnetic substances gets repelled, when placed in the magnetic
field.
•A charge in motion generates magnetic field, just like a charge at rest generates
an electric field.
•Magnetic field at a point r is denoted by B(r). It is a vector quantity, just like
electric field E(r) .
•Magnetic field can change with both distance and time .
•Magnetic field due to more than one source can be obtained by vectorial addition
of all sources. This is principle of superposition. This characteristic is also similar
to electric field.

7. Properties of Magnet :--
•Earth behaves as a magnet .
•When a bar magnet is freely suspended, it points to the NS direction .
•When two North poles are brought together, they repel each other.
Similar effect is observed for South pole also
•However, when a North pole and South pole is brought together,
they attract each other
•Magnetic monopoles do not exists which means we cannot have
a magnet with North pole alone or South pole alone
•If a bar magnet is broken in two halves, we get two similar bar magnets with weaker properties .
•With the help of iron and its alloys, we can make magnets

8. Magnetic field lines
•When iron fillings are sprinkled on a sheet of glass placed over a short bar magnet, we observe a
pattern. The pattern indicates that the magnet has two poles.
•This pictorially represents magnetic field lines. Thus, magnetic field lines are imaginary lines of
magnetic field inside and around the magnet.
Some of the properties of the magnetic field lines are :
1) They never intersect each other. If they intersect there must be two directions of the magnetic
field which is not possible .
2) The direction of magnetic field lines is from North pole to South pole outside the magnet and
from South pole to North pole inside the magnet.
3) The field lines emerge from the north pole and merge at the south pole.
4) Magnetic field lines are imaginary lines . Magnetic field lines are a visual tool used to
represent magnetic fields.
5) The density of the lines indicates the magnitude of the field. the magnetic field is stronger
and crowded near the poles of a magnet. As we move away from the poles it is weak and the
lines become less dense.
6) The magnetic field lines are continuous curve or closed loops .
7) More number of close lines indicate stronger magnetic field .
8) The tangent drawn at the field line gives the direction of the field at that point.

9. Magnetic effect by electric current or moving charge
The magnetic effect is observed by magnetic needle ( compass needle) which is a small bar
magnet.
Magnetic needle experience a torque on it in magnetic field, due to which It stays in a
particular direction .
The north pole of the magnetic needle is directed along the magnetic field B.
If magnetic field is uniform, at every point the needle will stays in same direction.
In non uniform magnetic field the magnetic needle will stay in different direction at different
points.
Magnetic Effect of Current :
An electric current (flow of electric charge) produces magnetic effect in the space around the
conductor called strength of Magnetic field or simply Magnetic field.

10. N
2. When current is flowing through a wire placed parallel to the
axis of a magnetic needle kept directly below the wire, the needle
will found to deflect towards west from its normal position.
K
N
K
I
E
3. When current is flowing in reverse direction through the wire, the
needle was found to deflect towards east in the opposite direction
to the earlier case.
Oersted’s Experiment:
E
E
I
S
S
S
N
1. When switch is open, current will not flowing through a wire
placed parallel to the axis of a magnetic needle kept directly
below the wire, the needle will not found to deflect from its normal
position.
In 1820, Oersted established the relationship between electricity
and magnetism. He concluded that a current carrying wire
produces a magnetic field around it.

11. On increasing the current in the circuit deflection of needle also increase.
Current carrying wire is electrically neutral so electric current around the wire is zero.
Therefor the deflection in the middle is due to magnetic field not due to electric field.
We can say that on passing current through a wire, a magnetic field is produced around the
wire whose direction depends on the direction of current and magnitude depends on the
magnitude of current hence electric current is produced due to moving charge so we can say
that moving charge produce magnetic field.
Note
1. An electric current or magnetic field directed towards inside the paper is represented by
cross.
2. An electric current or magnetic field directed coming outwords from the plane of the paper
is represented by Dot .
3. A moving charge produces both electric and magnetic field around it .
4. Stationary charge produces only electric field around it .
X
.

12. Right Hand palm Rule number 1
Stretch the fingers and Thumb of right hand at right angle
to each other then if the fingers point along the direction
of P and Thumb in the direction of current and normal to
the Palm will point in the direction of magnetic field .

13. BB
Rules to determine the direction of magnetic field:
Ampere’s Swimming Rule:
Ampere's swimming rule states that if a man swims along the wire
carrying current such that his face is always towards the magnetic
needle with current entering his feet and leaving his head then the
North Pole of the magnetic needle is always deflected towards his left
hand.
Maxwell’s Cork Screw Rule or Right Hand Screw Rule:
If a right handed cork screw is assumed to be held along the
conductor, and screw is rotated such that it moves in the direction of
the current, direction of magnetic field is same as that of the rotation
of screw.
It is also known as Maxwell's corkscrew rule or
Right handed corkscrew rule.
S
I
I I

14. Right Hand Thumb Rule or Curl Rule:
B
I
Stretch the fingers and Thumb of right hand at right angle to
each other then if the fingers point in the direction of field and
Thumb in the direction of current and normal to the Palm will
point in the direction of force .
Right Hand palm Rule number 2
This rule suggests that if you point the thumb of your right hand in the
direction of current flow in a current carrying conductor, and curl your fingers,
the direction in which your fingers will curl will be the direction of magnetic
field generated.
When the position of thumb will be upward the curled fingers will
be anti-clockwise and the magnetic field will be clockwise and
vice versa. The angle should be 90 degrees.