This is the chapter description of the physics chapter. will help you in understanding.

1. Magnetic effect of electric
current

2. 1. A thick copper wire XY is connected to an
electric circuit.
2.A small compass needle is placed
underneath
3.Note the position of the needle.
4. Current is passed through the
circuit by inserting the key in
the plug
5. The needle is observed
6. The compass needle gets deflected.
7. WHY SHOULD IT GET DEFLECTED?

3. 1. A mag. Needle gets deflected in
presence of a magnet, due to the
influence of mag. Field of bar magnet.
3. Therefore the deflection of mag.
needle kept under the current
carrying wire is due to the mag. field
produced by the wire.
3. Thus electricity and magnetism are
linked to each other.

4. A compass needle is a small bar Magnet.
A freely pivoted magnetic needle always point
approximately towards north- south direction.
(DIRECTIONAL PROPERTY)
The end pointing towards north is called north
seeking or north pole.
The end pointing towards south is called south
seeking or south pole.
Recapitulation - Magnetism

5. OTHER PROPERTIES
• Unlike poles Attract
• and like poles repel
• POLES EXIST IN PAIRS
• (MONO POLES DOES NOT EXIST)

6. Activity 1
1 A sheet of white paper is fixed on a
drawing board
2 A bar magnet is kept in the centre and
iron filings are uniformly sprinkled
around the bar magnet
3 The board is tapped gently.
4 The iron filings arrange themselves in
a pattern as shown.
5 This represents the magnetic field
around the magnet.
6 The iron filings arrange them selves due
to the force exerted by the bar magnet.
7 The field can be plotted using a
compass needle also.

7. The region surrounding a magnet , in which the force of
magnet can be detected is said to have a magnetic field.
Magnetic field is a quantity that has both magnitude and
direction.
The curved lines along which the iron filings align
themselves or the path along which the freely pivoted
magnetic needle moves is called the field lines or
magnetic lines of force.
The direction of the field is taken to be the direction in
which a north pole of the compass needle moves inside
it.

8. Characteristics of magnetic field
1. Strength of magnetic field is a quantity that can be
expressed both in magnitude and direction.
2. The relative strength of a magnetic field is shown by the
degree of closeness of magnetic field lines; (i.e. greater
the number of magnetic field lines in a unit space, more is
the strength of magnetic field)
3. The strength of magnetic field at a given point depends
upon its distance of from the poles of a bar magnet. (i.e.
more the distance, less is the strength of magnetic field.)

9. Characteristics of magnetic field line.
• 1. A magnetic field line can be defined as the path along which a
free north pole will move in a magnetic field.
• 2. Magnetic field lines are closed curves.
• 3. Magnetic field lines appear to start from N-pole and appear to
end at the south pole.
(within the magnet , they run from S- pole to N- north pole)
4. Magnetic field lines repel each other.
5. No two magnetic lines cut each other. ( If they intersect , a
compass needle placed at the intersection has to point two different
directions at the same time which is impossible.)

10. Magnetic field around a current carrying wire

11. Right-hand Thumb Rule
• When you wrap your
right hand around the
straight conductor
such that the thumb
points in the direction
of the current, the
fingers will wrap
around the conductor
in the direction of the
field lines of the
magnetic field..

12. Right Hand Thumb Rule

13. Magnetic field due to current through a
straight conductor.
 The current through a wire
produces a magnetic field.
 The shape of the magnetic
field lines for a straight
conductor is concentric
circles.
 These concentric circles
become larger as we move
away from the wire.

15. Magnetic field due to current in a straight
long conductor
1. Take a thick copper wire and
pass it through a horizontal card
board as shown.
2. Pass a strong current through the
wire.
3. Sprinkle iron filings on the
cardboard around the wire.
4. Tap the cardboard gently. You
would see a pattern as shown
here.
5. You may plot the field lines with
a compass needle also.

16. • 1. The magnetic field lines are in the form of
concentric circles near the conductor
2.Away from the conductor the field lines tend
to be elliptical due to the combined effect of
earth magnet and mag. Field due to the
conductor.
3.The direction of magnetic field lines reverses
with the reversal of the direction of current in
the conductor.
4.Increasing the strength of the current in the
conductor results in increase in mag. Field lines .

17. that is intensity of magnetic field increases
with the increase in strength of the current.
(No of magnetic field lines around the
conductor increases)
5. The magnetic field at a point decreases with
the increase in distance from the conductor.

18. Review Question
A current through a horizontal power line flows in east
to west direction. What is the direction of magnetic
field at a point directly below it and at a point directly
above it?
East
North south
West
Answer:
Below : North – South
Above : South to North

19. Magnetic field due to current in a circular
loop
Properties of magnetic field lines
1. The magnetic field lines are near
circular at the points where the
current enters or leaves the card board
2. Within the space enclosed by the coil,
the field lines are in same direction.
3. Near the centre of the coil, the
magnetic lines are almost parallel to
each other. Thus mag. Field near the
centre of the coil may be considered
uniform.
4. At the centre of the coil the plane of
magnetic field lines is at right angle to
the plane of the coil.
5. If there is a circular coil having n turns,
the field produced is n times as large
as that produced by a single turn ,as
the current in each turn has the same
direction and the field due to each turn
add up.

20. Solenoid
o A coil of many circular
turns of insulated
copper wire wrapped
closely in the shape of a
cylinder is called a
solenoid.
o A solenoid produces a
magnetic field when
electric current is
passed through it.
o The pattern of the
magnetic field lines
around a current-carrying
solenoid is similar to that
of a bar magnet.
o One end of the solenoid
is like a magnetic north
pole while the other is
like the south pole

21. MAGNETIC FIELD
PRODUCED BY A
SOLENOID

23. The strong magnetic field produced inside a solenoid can be used to
magnetize a piece of magnetic material like soft iron when placed inside a
coil. The magnet so formed is called an electromagnet.

24. Force on current carrying conductor
in a magnetic field
1. A aluminium rod AB is suspended
between the pole pieces of a horse
shoe magnet as shown.
3. A current is allowed to flow
through the conductor AB in the
direction from B to A
4. The conductor id found to get
deflected to the left as shown by
the arrow
5. When the poles of the magnet is
interchanged and when the current
is still from B to A, the force on the
conductor is found to be on the
right as shown.

25. 5.If the current is from A to B( Direction
is reversed) without reversing the pole
pieces of the magnet. The deflection of
the conductor(force) is to the left as
shown.
6. If the current is from A to B( Direction
is reversed) reversing the pole pieces of
the magnet.
The deflection of the
conductor(force) is to the
right as shown.

26. Force on a current-carrying conductor in a
magnetic field
• An electric current flowing through a conductor
produces a magnetic field. The field so produced
exerts a force on a magnet placed in the vicinity
of the conductor.
• The magnet also exerts an equal and opposite
force on the conductor.
• The magnitude of this force is highest when the
direction of current is at right angles to the
direction of the magnetic field.

27. • To Sum up
• The direction of force is reversed when the direction
of current through the conductor is reversed.
• The direction of force is also reversed by
interchanging the two poles of the magnet.

28. Fleming’s left-hand rule
• The directions of the current, force, and magnetic
field can be illustrated through a simple rule called
Fleming’s left-hand rule, if the direction of current is
at right angles to the direction of the magnetic field.
• According to this rule, stretch the thumb, forefinger,
and middle finger of your left hand such that they
are mutually perpendicular.
• The first finger points in the direction of the
magnetic field and the second finger in the direction
of the current, then the thumb will point in the
direction of motion or the force acting on the
conductor.