Download MAGNETIC EFFECT OF ELECTRIC CURRENT - class 10-j

MAGNETIC EFFECT OF
ELECTRIC CURRENT
• The force of attraction or repulsion in
and around a magnet is called
magnetism.
• Magnetite or lodestone is an ore of iron
– the magnet that is found in nature.
When a magnet is cutting into two parts
When a magnet is placed near a current carrying conductor
When there is no current
flowing through the circuit,
there is no deflection in the
magnetic compass.
When current flows
through the circuit, the
magnetic compass deflects.
Defining a magnetic field
Region around a magnet where its force can be felt is
known as the magnetic field.
Why does the iron fillings form pattern?
Due to the force exerted by the magnet, the iron filings
arrange themselves in patterns as shown above.
How is a magnetic field represented ?
Magnetic field is represented by
magnetic lines of forces (or) field
lines.
What are magnetic field lines ?
It is the path taken by a unit North pole when
placed in a magnetic field.
Magnetic field pattern due to a bar magnet
1. The field lines start from N-pole
and enter into the S-pole.
2. No two lines will intersect with
each other.
3. Inside the magnet the field lines
move from S-N pole.
4. The magnetic lines of forces are
crowded near the pole.
If you bring iron filings or iron nails close to a magnet,
the filings or nails will get attracted to the magnetic
poles. The centre of the magnet does not attract the
filings or the nails. Why ?
Because the magnetic lines of forces are crowded near the poles.
A current carrying straight conductor produces a
magnetic field –
An activity
How will you find the direction of the
magnetic field?
To determine the direction of the magnetic
field produced in a conductor carrying current
Right Hand Thumb Rule
Right Hand Thumb Rule
When a current carrying conductor is held in the
right hand,
so that the thumb is stretched along the direction
of the current,
then the fingers wrapped around the conductor
gives the direction of the magnetic field.
What happens when the direction of the current
through the conductor is reversed?
5. What happens to the
(i) number of magnetic field lines
(ii) magnetic field strength
When the current in the conductor increases?
Strength of the Magnetic Field
A stronger current will produce a
stronger magnetic field around the wire
as shown in Figure below.
Magnetic field pattern due to a circular loop
carrying current
The magnetic field strength at the
center of a circular coil carrying current
(i) Increases when the
Current flowing
through the coil
increases.
(ii) Increases as the
Number of turns of
the coil increases.
(iii) decreases as the
radius of the coil
increases.
A Solenoid
An insulated copper wire wound in the
form of a cylinder is called a solenoid.
A current carrying solenoid behaves as a
bar magnet.
Factors affecting the magnetic field strength due
to a current carrying solenoid
1. As the number of turns of the coil
increases, the magnetic field strength
also increases.
2. As the current flowing through the
solenoid increases , the magnetic
field strength also increases.
3. As a soft iron core is introduced in a
solenoid, the magnetic field
strength also increases.
Finding the polarity of the magnetic
field produced by a current carrying
solenoid
If the current flows in clockwise direction – S pole
If the current flows in anti-clockwise direction
– N Pole
• A current carrying conductor when placed in
a magnetic field experiences a force and then
moves.
State Fleming’s Left Hand rule .
• Stretch the thumb, the forefinger and the centre finger of
the left hand mutually
perpendicular to each other,
• the forefinger in the direction
of magnetic field,
• the centre finger in the
direction of current , then the
• thumb will point in the
direction of the force acting on
the conductor.
An Electric Motor