2. Electromagnetism
This is the type of a magnet that is
made from electricity.
There is a relationship between
electricity and magnetism.
Note; current carrying conductor
has magnetism around it.
3. Rules in Electromagnets
To determine the current or
field lines directions, use;
a. Maxwell’s cork screw rule
b. Right hand grip rule.
4. a. Maxwell’s cork screw rule
The direction of the screw
indicate direction of current
while the direction of force of
the thumb is the field lines of
force
6. b. Right hand grip rule
The direction of the thumb
indicate the current direction
while the rest of the fingers
points at the direction of the
magnetic field.
8. Fleming's Left Hand Rule
The thumb indication
direction of force, first finger
indicates magnetic field lines
force and the second finger
indicates current direction.
10. Current Conductor
The current carrying
conductor has magnetic field
around it.
This makes it experiences
some force when it passes
through magnets.
11. Current Conductor
To determine the direction of
force, Flemings left hand rule
is applied.
Next slide explains how this
rule is applied.
12. Fleming Left Hand Rule
a. Determine current direction
in the following diagrams;
13. Fleming Left Hand Rule
a. Determine direction of force
in the following diagrams;
14. Fleming Left Hand Rule
a. Determine magnetic poles in
the following diagrams;
15. Electromagnetic Induction
If current carrying conductor
cuts magnetic field e.m.f is
produced.
The principal is known as
electromagnetic induction.
19. 1. Faraday’s law
This states that the magnitude
of the induced e.m.f in a
conductor is directly
proportional to speed of
motion a magnet.
20. 2.Lenz’s law
This states that the induced e.m.f
is always acts to opposite to the
cause.
This means that induced current
flows in direction such that
opposes the change producing it.
23. 1. Electric motor
If the switch I closed, current
flows through the coil and
produces magnetic field.
The magnetic field in the coil
and that of permanent
magnet interact.
24. 1. Electric motor
The interaction causes push
on the left hand side of the
coil.
The coil rotates in a clockwise
direction and its momentum
carries it forward.
25. 1. Electric motor
The motor keeps on rotating
hence the motor effect.
The rotation can be reversed
by reversing current direction
.
39. 4.Moving Coil Microphone
This is the moving coil
microphone is a device for
changing sound energy into
electrical energy.
40. 4.Moving Coil Microphone
It has a diaphragm with alight
coil connected to it.
The coil is placed in between
two poles of magnet of a strong
cylindrical .
41. 4.Moving Coil Microphone
If a person speaks through a
microphone, sound energy sets
diaphragm into vibrations.
This moves the coil back and
forth between magnetic poles.
42. 4.Moving Coil Microphone
The process induces alternating
current that is amplified(made
larger) in the loud speaker.