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Magnetism and
Electromagnetism
MAGNETISM DAY 1
What causes magnetism?
How is magnetism linked to electric charges?
•  Magnetic fields come from
moving charges
•  a moving charge around an
atom produces a magnetic
field
•  currents in wires will produce
magnetic fields
•  The opposite is also true:
moving magnetic fields will
cause charges to move
(electromagnetic induction)
What causes magnetism?
How is magnetism linked to electric charges?
•  Magnetic forces are NOT the
same as electric forces.
•  How are they the same?
•  Like poles repel. Unlike poles
attract.
•  How are they different?
Magnetic poles always come
in pairs. You can’t separate a
North from South pole.
Domains and magnetism
• 
magnets—
an object that has an
alignment of domains
due to alignment of
atoms and their
magnetic dipoles
• 
ferromagnetic
materials (like iron) can
become magnetic near
a magnet because the
domains line up
Magnetic Poles
• 
• 
• 
magnetic pole—
where the magnetic
field is strongest
like poles repel
(North repels North
and South repels
South)
unlike poles attract
(North attracts
South)
Properties of Magnets
• 
• 
• 
cut a magnet in half and
you get two magnets
that still have a north
and south pole
heat it up or bang it
around and you weaken
the magnet by jumbling
domains
Make a magnet by
passing current through
iron (line up domains)
Earth’s magnetic field
•  Earth has a
magnetic field
because of a
rotating iron core
•  So why does a
North pole of a
compass point
North?
•  Because the
Earth’s magnetic
south pole is
located in
geographic North
Moving charged particles
Right Hand Rule #1
*Thumb in direction of current
*Fingers show how the
magnetic field wraps around
the wire
What does the magnetic field
look like around this wire?
Right hand rule #2
Force on a moving charge
FB = qv × B
Units:
Tesla (T)
Thumb = v = velocity of + charge (conventional current)
Fingers = B = direction of magnetic field
Palm = F = force on charge
X
= into the page
= out of the page
A positive particle is fired to the right through
a magnetic field directed into the page. What
is the resulting force on the particle?
Magnetic field into board
+
+
+
FB
+
+
v
v
+
+
Note speed never
changes; this
causes the
particle to curl.
Force is always
⊥ to v
What will be the direction of the
magnetic force on this proton?
What will be the direction of the
magnetic force on this proton?
2nd Right hand rule
A loop of wire is held inside a magnetic field
directed into the page as shown. The movable
bar is dragged to the right with a speed v. What
is the direction of the current in the loop?
MAGNETISM DAY 2
Electromagnet – electric
current creates a magnet
• 
making an
electromagnet—
wrap a current
carrying wire around
iron core and it will
set up a north and
south pole
Electromagnetic induction
Review…so far we’ve
seen that a moving
charge (a changing
electric field) produces
a magnetic field…the
opposite is also true….
Faraday’s Law
A changing magnetic
field will induce a
voltage in a wire (and a
resulting current)
Three every day Items that use
electromagnetic induction
Electric Motors
Electric Generators
Electric Transformers
Electric motors
• 
• 
Electromagnet in a
magnetic field will
rotate
electrical energy
used to produce
mechanical energy
Electromagnet
• 
making an
electromagnet—
wrap a current
carrying wire around
iron core and it will
set up a north and
south pole
Electric motors
Electromagnet in a
magnetic field will rotate
(kinetic energy)
electrical energy is used
to produce mechanical
energy
Electric motor
Commutator ring
Commutator allows
the current in the
electromagnet to
switch directions so
the motor shaft spins
continuously
Electric Generator
Uses mechanical energy to
rotate wires in a magnetic
field to produce electrical
energy
Coil flip-flops so this
produces an Alternating
Current (AC) in the wire
Burn coal or use nuclear
power to create steam from
water to turn coils
Wind and water just turn the
turbines directly
Something
has to turn
the coils
Electric Transformers
Alternating electrical current on
one side produces a magnetic
field which induces a voltage in
the other side of the
transformer
Steps up voltage with more
windings on other side
Steps down voltage with
fewer windings on other side
Power and energy are
conserved! Remember, you
can’t make more energy.
Putting it all together…
Spinning turbines
and generators are
inside this power
plant
Electromagnet
• 
making an
electromagnet—
wrap a current
carrying wire around
iron core and it will
set up a north and
south pole