Michael Faraday devised the world’s first electric generator in 1821. The generator he built was a seemingly simple thing: a hand-cranked copper disk rotated between the poles of a permanent magnet. DC GENERATOR Are used in recharging automobile batteries. A direct-current (DC) generator is a rotating machine that supplies an electrical output with unidirectional voltage and current. The field is produced by direct current in field coils or by permanent magnets on the stator. The output, or armature, windings are placed in slots in the cylindrical iron rotor. AC GENERATOR Are used in recharging automobile batteries. A direct-current (DC) generator is a rotating machine that supplies an electrical output with unidirectional voltage and current. The field is produced by direct current in field coils or by permanent magnets on the stator. The output, or armature, windings are placed in slots in the cylindrical iron rotor. MOTORS AND GENERATORS Compare the illustrations of a dynamo and a DC motor. The action of the dynamo is just the reverse of the action of a motor, The similarity between these two was not recognized until the mid-nineteenth century when an “accident” happened at the Vienna Exposition Hall in 1873. The 2nd dynamo began to spark and whine and come live. The dynamo had become a generator. The versatility of a device to act as a motor at one time and a generator at other times can be used to great advantage. In France and Australia, trains running uphill or on level ground are fueled by electricity from power lines. When the train moves downhill, however, its motor becomes a generator. The power generated is sent to the power lines to be used by other trains. This maintains a cycle of changes from gravitational potential energy to electrical energy.

1. FARADAY’S DYNAMO
Michael Faraday devised
the world’s first electric
generator in 1821. The
generator he built was a
seemingly simple thing: a
hand-cranked copper
disk rotated between the
poles of a permanent
magnet.

3. THIS IS HOW FARADAYS GENERATOR OR
DYNAMO WORKS

4. DC GENERATORS
 Are used in recharging automobile
batteries.
 A direct-current (DC) generator is a
rotating machine that supplies an
electrical output with unidirectional
voltage and current.
 The field is produced by direct current in
field coils or by permanent magnets on
the stator. The output, or armature,
windings are placed in slots in the

5. The current / vs time t graph for a single coil DC generator
(a) Cross
sectional view
of a single coil
(b) The pulsating
DC from a single-
coil generator

6. Possible positions of the single-loop DC generator
in the magnetic field showing the direction of the
current in the loop and in the external circuit.

7. (a) Profile of a
three-coil DC
generator.
(b) The voltage-time graph for
the three-coil DC generator.

9. AC GENERATORS
 Are used in electric power plants.
 An AC generator is an electric device that
produces an alternating current, which is
electric current that reverses direction
several times every second. Such
generators are also known as
synchronous generators or alternators.

10. (a)A simple AC generator.
(b) A graph showing current at different positions of
the loop.

11. -At position P, the
current in the circuit
connected to the loop
is counterclockwise.
- At position R,
the current in the
circuit connected
to the loop is
clockwise.

12. The direction of AC reverses every
half cycle.

14. MOTORS AND GENERATORS
 Compare the illustrations of a dynamo and a DC
motor. The action of the dynamo is just the reverse
of the action of a motor,
 The similarity between these two was not
recognized until the mid-nineteenth century when
an “accident” happened at the Vienna Exposition
Hall in 1873.
 The 2nd dynamo began to spark and whine and
come live. The dynamo had become a generator.
 The versatility of a device to act as a motor at one
time and a generator at other times can be used to
great advantage.

15.  In France and Australia, trains running uphill or on
level ground are fueled by electricity from power
lines. When the train moves downhill, however, its
motor becomes a generator. The power generated is
sent to the power lines to be used by other trains.
This maintains a cycle of changes from gravitational
potential energy to electrical energy.