This document discusses the relationship between magnetism and electricity, and how this relationship led to the development of motors. It explains that Michael Faraday discovered that a current-carrying conductor in a magnetic field experiences a force perpendicular to both the magnetic field and current direction. This effect is known as the Lorentz force. The magnitude of the Lorentz force depends on the current, magnetic field strength, and length of conductor in the field. This relationship between electricity, magnetism and force allowed for the development of electromagnets and electric motors, which have since become widely used in factories and homes.

1. Chapter 9
FROM MAGNETS
TO
MOTORS

2. FROM MAGNETS TO MOTORS
The movement of the compass needle away
from the magnetic poles and the alignment of
the iron filing along magnetic field lines could
only have happened as a result of the forces
acting on them.
A current-carrying wire moved normally away
or toward when placed in between the poles
of a U magnet depending on the orientation of
the magnets and the current.
The movements always show a perpendicular
pattern (right angle) between B and I.

3. FROM MAGNETS TO MOTORS
Michael Faraday himself noticed that
whenever a current-carrying conductor is in
a magnetic field, it tended to move in a
direction at right angles to both the direction
of I and B.
B
F
I B
F
I

4. This illustration shows magnetic field
resulting from the interaction between the
external magnetic field and the magnetic
field around the current-carrying conductor.
FROM MAGNETS TO MOTORS
I N
S
BF

5. The N and S poles of the U magnet exert a
stronger magnetic field, while the conductor with
current exerts a weaker magnetic field.
The movements of the conductor between the
poles depend the direction of the current.
FROM MAGNETS TO MOTORS
I N
S
BF

6. The force experienced by a conductor is
maximum when current I (the velocity of
electrons) and the magnetic field
directions are perpendicular to each other.
*The magnitude of the force F further
depends on:
1. the current I in the conductor;
2. the strength of the magnetic field B; and
3. the length L of the conductor that lies in
the magnetic field.
FROM MAGNETS TO MOTORS

7. The magnitude of F is equal to the product
of B, I, and L. Written as…
F = B.I.L
when the wire is perpendicular to B.
I is in Amperes (A), L is in meter (m), B is
in newton/ampere-meter, F is expressed
in newton (N).
The standard unit of magnetic field is
expressed also in Testa (T).
FROM MAGNETS TO MOTORS

8. FROM MAGNETS TO MOTORS

9. FROM MAGNETS TO MOTORS

10. This is a simple structure of a motor.
FROM MAGNETS TO MOTORS

11. Magnets can paint pictures.
Painting TV pictures also employs magnets.
Outside a television picture tube are
magnets. The picture tube is an evacuated
tube. As the beam of electrons move from
the electron gun to the screen, it is deflected
by the horizontal and vertical magnets.
The amount of deflection of the electron
beam depends on the force exerted on the
electrons.
FROM MAGNETS TO MOTORS

12. FROM MAGNETS TO MOTORS

13. FROM MAGNETS TO MOTORS

14. FROM MAGNETS TO MOTORS

15. FROM MAGNETS TO MOTORS

16. FROM MAGNETS TO MOTORS
The discovery of the relationship between
electricity and magnetism ushered in the age
of electricity. The fact that current produces
magnetism became the basis of
electromagnets. Electromagnets in turn gave
rise to wireless communication.
Magnetism produced by currents interacts
with external magnetic fields. This concept
gave rise to motors. Motors can be found in
factories and at home. Motor has gone a
long way in giving convenience to our daily