ppt

1. B.J.P.S Samiti’s
M.V.HERWADKAR ENGLISH MEDIUM HIGH SCHOOL
Magnetic Effect of Electricity
Program:
Semester:
Course: NAME OF THE COURSE
1

2. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
2
 Magnet is an object that attracts objects made of iron,
cobalt and nickel. Magnet comes to rest in North – South
direction, when suspended freely.
 Properties of Magnet
 A free suspended magnet always points towards the
north and south direction.
 The pole of a magnet which points toward north direction
is called north pole or north-seeking.
 The pole of a magnet which points toward south
direction is called south pole or south seeking.
 Like poles of magnets repel each other while unlike
poles of magnets attract each other
:

3. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
3

4. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
4

5. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
5
 Magnetic field: The area around a magnet where a
magnetic force is experienced is called the magnetic
field. It is a quantity that has both direction and
magnitude, (i.e., Vector quantity).
 Magnetic field lines :-Magnetic field lines are the paths
around a magnet along which the north pole of a
magnetic compass needle tends to move.

6. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
6
 Properties of magnetic field lines:
i) The magnetic field lines emerge at the north pole and
merge at the south pole outside the magnet.
ii) The magnetic field lines moves from south pole to
the north pole inside the magnet
iii) The magnetic field lines are closer at the poles.
iv) The magnetic field lines do not intersect each other.
v)Field lines are closed curves.

7. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
7

8. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
8

9. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
9
 Magnetic field due to a current carrying conductor :-
 If a magnetic compass is placed near a conductor carrying
current (wire), the needle is deflected. This shows that a
conductor carrying current has a magnetic field around it.
 The magnetic field around a current carrying straight conductor
is in concentric circles.
 The direction of magnetic field through a current carrying
conductor depends upon the direction of flow electric current.
The direction of magnetic field, in relation to
direction of electric current through a straight
conductor can be depicted by using the Right Hand
Thumb Rule.

10. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
10
Right hand thumb rule :-
 It states that ‘ If a current carrying conductor is held in
the right hand such that the thumb points in the
direction of current, then the fingers wrapped around
the conductor shows the direction of the magnetic field
’.

11. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
11
 Properties of magnetic field through a straight conductor:
 The magnitude of magnetic field increases with increase in electric
current and decreases with decrease in electric current.
 The magnitude of magnetic field decreases with increase in
distance and vice – versa. The size of concentric circles of magnetic
field lines increases with distance from the conductor, which shows
that magnetic field decreases with distance.
 Magnetic field lines are always parallel to each other.
 No two field lines cross each other.

12. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
12
 Magnetic field due to a current through a circular loop :
When current is passed through a circular conductor (loop) the
magnetic field produced is in the form of concentric circles around
the conductor. Towards the centre the arcs of the circles become
larger and appears as straight line.


13. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
13
 Properties of magnetic field through a circular loop:
 The magnetic field lines are concentric circles at every point of a
current-carrying circular loop
 The magnetic field lines are straight at the center of the loop
 At the center of the loop, the intensity of the magnetic field is
maximum while the magnetic field intensity decreases as we move
away from the center of the loop
 The magnitude of the magnetic field is directly proportional to the
magnitude of current through the loop. i.e. B∝.I .
 The magnitude of the magnetic field is inversely proportional to the
radius of the circular loop. i.e. B∝1/r.
 The magnitude of the magnetic field also depends upon the number
of turns in the current-carrying loop. The larger the number of turns,
the higher the magnitude of the magnetic field.

14. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
14
 Magnetic field due to current in a solenoid :-
 A coil of many circular turns of insulated copper wire wound on a cylindrical
insulating body .
 When current flows through a solenoid, it behaves like a bar magnet. The ends
of the solenoid behaves like the North and South poles of a magnet. The
magnetic field produced by a solenoid is similar to the magnetic field produced
by a bar magnet.
 The field lines inside the solenoid are parallel and magnetic field inside the
solenoid is uniform
 The strength of the magnetic field depends upon the strength of the current and
the number of turns of the coil.


15. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
15
 Electromagnet :-
 A strong magnetic field inside a solenoid can be used to
magnetize a piece of magnetic material like a soft iron when
placed inside the coil. Such a magnet is called an electromagnet.

( )

16. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
16
 Force on a conductor carrying current in a magnetic field :-
 A.M.Ampere suggested that if a current carrying conductor produces a
magnetic field and exerts a force on a magnet, then a magnet should also
exerts a force on a current carrying conductor.
 Eg :- If an aluminum rod is suspended horizontally by a wire between the
poles of a horse shoe magnet and current is passed through the wire, then
the aluminum rod is displaced.
 If the direction of current is reversed, the direction of displacement is also
reversed. The force exerted is maximum if the conductor is perpendicular
to the magnetic field.


17. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
17

18. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
18
 Fleming’s Left Hand Rule :- The direction of force (motion) of a
current carrying conductor in a magnetic field is given by Fleming’s
Left Hand Rule.
 It states that ‘ If we hold the thumb, fore finger and middle finger of
the left hand perpendicular to each other such that
i)the fore finger points in the direction of magnetic field,
ii) the middle finger points in the direction of current, then
iii)the thumb shows the direction of force (motion) of the conductor’.


19. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
19
 Electric Motor: is a device which converts electrical energy into
mechanical energy.
 Principle of Electric Motor
The principle of the electric motor is based on the fact that a current
carrying conductor produces a magnetic field around it. A current
carrying conductor placed perpendicular to magnetic field
experiences a force.
 Construction of Electric Motor

20. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
20
 Electromagnetic induction:- (Michael Faraday)
 The motion of a magnet with respect to a coil or a change in the magnetic
field induce a potential difference in the coil and produces induced
current. This is called electromagnetic induction.
 Motion of a magnet with respect to a coil produces induced current:
 If a magnet is moved towards or away from a coil of wire connected to a
galvanometer, the galvanometer needle shows a deflection. This shows
that current is induced in the coil due to the motion of the magnet.


21. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
21
 Change in magnetic field produces induced current :-
 Take two coils of wires wound around a cylindrical paper roll. Connect
one coil to a battery and the other coil to a galvanometer(instrument that
detects the presence and direction of current in circuit).
 If current is passed through the first coil, the galvanometer needle
shows a deflection in the second coil.
 If the current is disconnected, the needle moves in the opposite
direction.
 This shows that current is induced due to change in magnetic field.

22. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
22
 Fleming’s Right Hand Rule :-The direction of induced current is
given by Fleming’s Right Hand Rule.
 It states that ‘ If the thumb, fore finger and middle finger of the right
hand is held perpendicular to each other such that
i) the thumb points in the direction of motion of the conductor
ii) the fore finger points in the direction of the magnetic field then
iii) the middle finger shows the direction of induced current ’.


23. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
23
 Electric Generator: It is a machine that converts
mechanical energy into electrical energy.
 Working Principle of generator: The electric generator works
on the principle of electromagnetic induction i.e., when a coil is
rotated in the presence of a uniform magnetic field, the current is
induced in it.
 Construction of generator:

24. 24
 Direct and Alternating current :-
 Direct current (DC) :- A current that always flows in one direction
only is called direct current.
 The current we get from a battery is a direct current.
 Alternating current (AC) :- A current that reverses its direction
periodically is called alternating current.
 Most power stations in our country produce alternating current.
 AC changes direction every 1/100 second and its frequency is 50 Hertz
 One advantage of AC over DC is that it can be transmitted over long
distances without much loss of energy.

25. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
25
 .

26. 26
 Domestic electric circuit :-
 Electric power to homes is supplied through the mains.
 It has two wires. One is a live wire (positive wire) with red insulation and
the other is a neutral wire (negative wire) with black insulation.
 The potential difference between the two wires is 220V. The earth wire
with green insulation is connected to a metal plate kept in the ground.
 Two separate circuits are used. One is of 15A for appliances with high
power rating like gysers, air conditioners etc. The other is of 5A for fans,
bulbs etc.
 The different appliances are connected in parallel so that every appliance
gets equal voltage and even if one is switched off the others are not
affected.
 The appliances having metallic body like electric iron, refrigerators etc.,
their metallic body is connected to the earth wire so that if there is
leakage of current, it passes to the earth and prevents electric shock.

27. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
27
Electric fuse :-
 Electric fuse is a safety device used in electric circuits to protect the
circuit and appliances from damage due to overloading and short circuit.
 It is a wire having high resistance and low melting point.
 If excess current flows through the circuit, the fuse wire melts and breaks
the circuit.
 Fuse wire is made of a metal or an alloy of metals like lead, tin,
aluminium and copper.
 Fuse wire is connected in series with the live wire.

28. M.V.HERWADKAR ENGLISH MEDIUM SCHOOL
28
 Overloading :-
 Overloading is caused due to increase in voltage, or if the live wire and
neutral wire comes in contact or if too many appliances are connected to a
single socket.
 It results in overheating of the wires and can cause damage to the circuit
and appliances.
 Short circuit :-
 Short circuit is caused when the live wire and neutral wire comes in
contact and the current suddenly increases in the circuit. It causes spark,
fire and damage to the circuit and appliances.