The document discusses Fleming's left hand rule and right hand rule for electric motors and generators. It then provides explanations of how electric motors and generators work. It states that an electric motor converts electrical energy to mechanical energy using the principles that a current-carrying coil placed in a magnetic field will experience a force. It also discusses the construction and working of DC motors and AC generators. The key components of motors and generators like armature, commutator, and brushes are explained. Faraday's law of electromagnetic induction and his experiment demonstrating it are also summarized.

3. Fleming’s
Left Hand Rule
(Electric Motor)

4. 

5.  If the forefinger, middle finger and thumb of the left
hand are stretched such that they are at right angles
to each other, then:
 The forefinger gives the direction of the magnetic field.
 The middle finger points in the direction of the current.
 The thumb gives the direction of the force acting on the
current-carrying conductor placed in the external magnetic field.

6. Electric Motor

7. 
Electric Motor
An electric motor is an electrical machine that
converts electrical energy into mechanical energy. An
Electric Motor is based on the principle that when a
rectangular coil is placed in magnetic field and current is
passed through it, two equal and opposite forces act on the
coil which rotates it continuously.

8. Construction of
Electric Motor :-
It Consist of a coil, say ABCD connected
to a source of current and a switch. The
commutators R1 and R2 are fixed to the
coil and pressed tightly against brushes
B1 and B2. The function of Commutator
is to reverse the direction of current
flowing through the coil every time the
coil passes the vertical position, i.e.,
after half rotation in electric motor. In
Electric motor. Commutators acts as
split rings.

9. Above images helps in understanding the working principle of a Electric
motor. When armature windings are connected to a DC supply, current sets up in
the winding. Magnetic field may be provided by field winding (electromagnetism)
or by using permanent magnets. In this case, current carrying armature
conductors experience force due to the magnetic field, according to the principle
stated above.
Commutator is made segmented to achieve unidirectional torque. Otherwise, the
direction of force would have reversed every time when the direction of
movement of conductor is reversed the magnetic field.
This is how a Electric motor works!

10. The speed of rotation of the motor can be increased by :-
 Increasing the strength of the current through armature
 Increasing the number of turns in the coil of armature.
 Increasing the area of the coil
 Increasing the strength of magnetic field

11. Uses of Electric Motor :-
Motors have a wide variety of uses and are found in cars, clocks,
drills, fans, fridges, hair dryers, toothbrushes, vacuum
cleaners, water pumps (for fish tanks, central heating, fire fighting) washing machines, hard disk drives, DVD
players,
electric vehicles and industrial equipment including extruder,
fork-lift trucks, lathes, mills, hoists, robots and winches.
We would expect the efficiency of a motor to be
between 70 and 85%. The wasted energy is heat and sound.

12. Fleming’s
Right Hand Rule
(Electric Generator)

14.  If the forefinger, middle finger and thumb of the Right
hand are stretched such that they are at right angles to
each other, then:
Fleming's right-hand rule (for generators) shows the direction of induced
current when a conductor moves in a magnetic field. It can be used to determine
the direction of current in a generator's windings.
When a conductor such as a wire attached to a circuit moves through a magnetic
field, an electric current is induced in the wire due to Faraday's law of induction.
The current in the wire can have two possible directions. Fleming's right-hand rule
gives which direction the current flows
The right hand is held with the thumb, first finger and second finger mutually
perpendicular to each other (at right angles), as shown in the diagram.
The thumb is pointed in the direction of motion of
the conductor.
The first finger is pointed in the direction of the
magnetic field. (north to south).
Then the second finger represents the direction of
the induced or generated current (the direction of the
induced current will be the direction of conventional
current; from positive to negative).

15. Electric
Generator

16. Electric
Generator
In Electricity Generation, a generator is a device that converts mechanical
energy to electric 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.
The reverse conversion of electrical energy into mechanical energy is done by
an electric motor, and motors and generators have many similarities. Many
motors can be mechanically driven to generate electricity and frequently make
acceptable generators.

17. 
D.C. Generator

18. D.C. Generator
A dc generator is an electrical machine which converts mechanical energy
into direct current electricity. This energy conversion is based on the
principle of production of dynamically induced E.M.F. According
to Faradays law of induction, whenever a conductor is placed in a varying
magnetic field (OR a conductor is moved in a magnetic field), an emf
(electromotive force) gets induced in the conductor. The magnitude of
induced emf can be calculated from the emf equation of dc generator. If
the conductor is provided with the closed path, the induced current will
circulate within the path. In a DC generator, field coils produce
an electromagnetic field and the armature conductors are rotated into the
field. Thus, an electromagnetically induced emf is generated in the
armature conductors. The direction of induced current is given by Fleming
right hand rule.

19. A.C. Generator
An alternator is an electrical machine which converts mechanical energy into
alternating electric energy. They are also known as synchronous generators.
The working principle of an alternator or AC generator is similar to the basic
working principle of a DC generator.Above figure helps you understanding how an
alternator or AC generator works. According to
the Faraday's law of electromagnetic induction,
whenever a conductor moves in a magnetic field EMF
gets induced across the conductor. If the close path is
provided to the conductor, induced emf causes current
to flow in the circuit.
Now, see the above figure. Let the conductor coil
ABCD is placed in a magnetic field. The direction of magnetic flux will be form N pole
to S pole. The coil is connected to slip rings, and the load is connected through
brushes resting on the slip rings.
Now, consider the case 1 from above figure. The coil is rotating clockwise, in this case
the direction of induced current can be given by Fleming's right hand rule, and it will be
along A-B-C-D. As the coil is rotating clockwise, after half of the time period, the
position of the coil will be as in second case of above figure. In this case, the direction

21. In 1831, Michael Faraday, an English physicist gave one of the most basic laws of
electromagnetism called Faraday's law of electromagnetic induction. This law
explains the working principle of most of theelectrical motors, generators, electrical
transformers and inductors . This law shows the relationship between electric circuit
and magnetic field. Faraday performs an experiment with a magnet and coil. During
this experiment, he found how emf is induced in the coil when flux linked with it
changes. He has also done experiments in electro-chemistry and electrolysis.
Faraday's Experiment:-

22. Faraday's Experiment:-
In this experiment, Faraday takes a magnet and a coil and connects a
galvanometer across the coil. At starting, the magnet is at rest, so there
is no deflection in the galvanometer i.e needle of galvanometer is at the
center or zero position. When the magnet is moved towards the coil,
the needle of galvanometer deflects in one direction. When the magnet
is held stationary at that position, the needle of galvanometer returns
back to zero position. Now when the magnet is moved away from the
coil, there is some deflection in the needle but in opposite direction and
again when the magnet becomes stationary, at that point with respect
to coil, the needle of the galvanometer returns back to the zero
position. Similarly, if magnet is held stationary and the coil is moved
away and towards the magnet, the galvanometer shows deflection in
similar manner. It is also seen that, the faster the change in the
magnetic field, the greater will be the induced emf or voltage in the coil.

23. Position of magnet Deflection in galvanometer
Magnet at rest No deflection in galvanometer
Magnet moves towards the coil
Deflection in galvanometer in
one direction
Magnet is held stationary at
same position (near the coil)
No deflection in galvanometer
Magnet moves away from the
coil
Deflection in galvanometer but
in opposite direction
Magnet is held stationary at
same position (away from the
coil)
No deflection in galvanometer

26. MuttuRaj Yangi
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