1. Magnetic Effects of Electric Current

2. • When an electric current passes
through a wire, a magnetic field is
produced around the wire. If the wire is
wound into a coil the resulting field is
similar to that of a bar magnet wit north
and south poles.
The magnetic effect of an electric current.

3. • A compass needle is, in fact, a small bar
magnet. The end of the compass needle
point approx. towards north and south
directions. The end pointing towards north is
called north seeking or north pole . The other
end points towards south is called south
seeking or south pole .
 Like poles repel, while unlike poles of
magnets attract each other
MAGNETIC FIELD AND FIELD LINES

4. • Fix a sheet of white paper on a drawing board using
some adhesive material.
• Place a bar magnet in the centre of it.
• Sprinkle some iron filings uniformly around the bar
magnet . A salt-sprinkler may be used for this
purpose .
• Now tap the board gently.
• What do you observe?
Activity to show magnetic field and field line

5. Observation
• The magnet exerts its influence in the region
surrounding it. Therefore the iron filings
experience a force. The force thus exerted
makes iron filings to arrange in a pattern. The
region surrounding a magnet, in which the
force of the magnet can be detected, is said
to have a magnetic field. The lines along
which the iron filings align themselves
represent magnetic field lines.

6. Magnetic Field
• Magnetic field is a quantity that has both direction and
magnitude.
• The direction of the magnetic field is taken to be the direction
in which a north pole of the compass needle moves inside it.
Therefore it is taken by convention that the field lines emerge
from north pole and merge at the south pole.
• Inside the magnet, the direction of field lines is from its south
pole to its north pole. Thus the magnetic field lines are closed
curves.

8. • A convenient way of finding the direction of magnetic
field associated with a current-carrying conductor is –
 Imagine that you are holding a current-carrying straight
conductor in your right hand such that thumb point
toward the direction of current. Then your fingers will
wrap around the conductor in the direction of the field
lines of magnetic field. This is known as right-hand thumb
rule. And this is also known as Maxwell’s screw law.
Right-Hand Thumb Rule

9. • We know that the magnetic field produced by a
current-carrying straight wire depends inversely on the
distance from it. Similarly at every point of a current-
carrying circular loop, the concentric circle
representing the magnetic field around it would
become larger and larger as we move away from the
wire. By the time we reach at the centre of the circular
loop, the arcs of these big circles would appear as
straight lines.
Every point on the wire carrying current would give rise
to the magnetic field appearing as straight lines at the
centre of the loop.
Magnetic Field due to a Current through a
circular loop

10. Magnetic Field due to a Current in a
Solenoid
• A coil of many circular turns of insulated
copper wire wrapped closely in the shape of
a cylinder is called a solenoid.
• The field lines inside the solenoid are in the
form of parallel straight lines. This indicates
that the magnetic field is the same at all
points inside the solenoid. That is, the field is
uniform inside the solenoid.

11. • A strong magnetic field produced inside a
solenoid can be used to magnetise a piece of
magnetic material, like soft iron, when placed
inside the coil. The magnet so formed is
called an electromagnet.
Electromagnet

12. Applications of electromagnets
• To lift iron rods and steel bars.
• As cranes in scrap yards
• In hospitals to remove splinters from
eyes.
• In electric bells
• In the cores of transmissions
• In control systems.

13. Electric Motor
• An electric motor is a rotating device that
converts electrical energy into mechanical
energy . Electric motor is used as an important
component in electric fans , refrigerators,
mixers, washing machines , computers etc.
• A device that reverses the direction of flow of
current through a circuit is called a
commutator .

14. • Electromagnetic or Magnetic induction is the
production of an electromotive force or voltage
across an electrical conductor due to its dynamic
interaction with a magnetic field. Michael Faraday is
generally credited with the discovery of induction in
1831, and mathematically described it as Faraday's
law of induction.
Electromagnetic Induction

15. • Galvanometer is the historical name given to
a moving coil electric current detector. When
a current is passed through a coil in a
magnetic field, the coil experiences a torque
proportional to the current.
Galvanometer

16. • In electricity generation, a generator is a device
that converts mechanical energy
to electrical energy for use in an external circuit.
The source of mechanical energy may vary widely
from a hand crank to an internal combustion
engine. Generators provide nearly all of the
power for electric power grids.
Electric Generator

17. Domestic Electric CircuitsA DOMESTIC ELECTRIC CIRCUT