PHYSICS STUDY GUIDE
CHAPTER 14: MAGNETISM
WHAT YOU NEED TO KNOW
1. Magnets were first used by early Chinese and Greek civilizations.
2. Magnets are similar to electric charges, because both create a field that distorts space around them.
3. Magnetic poles are located at each end of a bar magnet (or the endings of a horse magnet).
4. A horseshoe magnet is magnet is a bar magnet that has been bent in the shape of a horseshoe.
5. Opposite poles attract and like poles repel.
6. Magnets are different from electric charges, because electric charges can be isolated (electron and
proton), whereas a single magnetic pole has never been isolated. Magnetic poles are always found in
pairs.
7. If a magnet is broken in pieces, each piece becomes an independent magnet with its own north and
South Poles.
8. Locate the North and south poles on the magnet before and after it is broken in two pieces
9. A compass is a magnet with a needle that moves freely. Compasses are used to detect magnetic fields.
10. The biggest magnet on Earth is the Earth itself, due to its rotating core made of iron and Nickel. On
Earth the north magnetic pole coincides with the south geographical pole and the south magnetic pole
coincides with the north geographical pole
11. Physical quantity
NAME OF PHYSICAL
QUANTITY
SYMBOL
UNITS
TYPE OF PHYSICAL QUANTITY
Magnetic Field
B
Tesla (T)
Vector
The units for magnetic field were named after the last name of Nikola Tesla, a Serbian-American Engineer
who made revolutionary developments in the field of electromagnetism.
12. Permanent magnets can be made only of three different metals: Iron, Nickel, or Cobalt.
13. Electrons inside of materials such as iron, nickel or cobalt stick together and align themselves into
small regions of more or less uniform alignment called magnetic domains or Weiss domains. When
domains are aligned these metals behave like magnets.
Domains before magnetization
Domains before magnetization
14. Two ways to produce a permanent magnet are rubbing iron or nickel or cobalt against a magnet o
placing one of these elements inside a strong magnetic field.
15. Two reasons why a magnet can become weaker are by dropping the magnet or by heating the
magnet.
16. In 1819 Hans Christian Ørsted a Danish Physicist, discover that an electric current carrying wire
deflects the needle of a compass placed near it.
17. Two different ways (sources) to obtain a magnetic field are: a permanent magnet and an electric
current carrying wire.
18. In a permanent magnet, the direction of the magnetic field lines outside the magnet is set to be
ALWAYS from north to south.
19. In an electric current carrying wire, the shape of the magnetic field lines is concentric circles around
the wire and its direction is given by the way your right hand naturally curl its fingers around your
thumb.
MAGNETIC FORCE EXERTED BY A MAGNETIC FIELD ON A CHARGED PARTICLE
The magnetic force felt by a particle will be perpendicular to the particle’s velocity, and also perpendicular
to the magnetic field.
FB = B · v · q
SYMBOL
FB
B
v
q
NAME
Magnetic Force exerted on the charge
Magnitude of the magnetic field of the magnet
Velocity of the charged particle
Magnitude of the charge
UNITS
Newton
Tesla
Meters per second
Coulombs
B
FB
Right
§
§
§
v
Hand Rule #2
Thumb: points in the direction of the VELOCITY of the particle.
Fingers: Point in the direction of the magnetic field
Magnetic Force:
o Negative particle: Direction of magnetic Force is out of palm
o Positive particle: Direction of magnetic force is into the palm
UNITS SYMBOL
N
T
m/s
C
MAGNETIC FORCE EXERTED BY A MAGNETIC FIELD ON AN ELECTRIC CURRENT CARRYING WIRE
The magnetic force felt by an electric current carrying wire will be perpendicular to the electric current,
and also perpendicular to the magnetic field.
FB = L · B · I
SYMBOL
FB
L
B
I
NAME
Magnetic Force exerted on the charge
Length of the wire
Magnitude of the magnetic field of the magnet
Magnitude of the electric current
UNITS
Newton
Meters
Tesla
Amperes
B
FB
Right
§
§
§
I
Hand Rule #2
Thumb: points in the direction of the ELECTRIC CURRENT (I).
Fingers: Point in the direction of the MAGNETIC FIELD (B).
Out of palm: Points in the direction of the MAGNETIC FORCE (FB).
UNITS SYMBOL
N
m
T
A