Conceptual Physics, no math.

1. Magnetism
2000 years ago, rocks in Magnesia, Greece were found
to have weird properties. Later called “lodestones.”
Hans Christian Oersted
(Danish Science Professor, 1820)
 Discovered relationship
between electricity and
magnetism accidentally while
demonstrating electric currents.
These caused a compass needle
to tip.

2. Similarities to Electricity
• Exert non-contact force
– Has a Field
• Strength of force depends on distance
• Attract and Repel ∴ there are 2 parts (north & south)
– Opposites attract -- Like pole repel
Differences from Electricity
• You can get 1 e by itself. You can never get a
North pole without a South Pole and vice versa.
S NS N S N S N

3. Magnets & Electricity
• Electrons & magnetic fields
– Remember electron spin?
• Charge in motion causes a small magnetic field.
– Many electrons spinning in same direction
produces …
• Magnetic Domains
– Clusters of aligned electrons spinning in the
same direction
– How is a weak magnet different from a strong
magnet?
• Stronger magnets have more aligned domains

4. Magnetic Domains
How strong are these magnets? Why?

5. Magnetic Field (B)
 Area around a magnet that affects other magnetic objects.
Measured in Teslas (T)
Vector or Scalar?
N S
Rules for drawing
Leaves Object perpendicular
Out of North into South
more lines stronger field
Field is strongest at the poles
Magnetic Force caused by Magnetic Field
F = q v B
– qelectron & proton = 1.6 x 10-19 C

6. 1st Right Hand Rule
Direction of the magnetic force is perpendicular to
the velocity and the field
1st Right Hand Rule (3 Dimensions)
 Tells you the direction of the force.
• Place your fingers in the direction of B
• your thumb in the direction of v
• palm tells direction of the force
• out of + into –
Since this deals with 3 Dimensions…
mean going into the page (feathers of an
arrow)
mean coming out of the page (arrowhead)

7. • Find the direction of the force for each of
the following on a proton.
v B B
Bout
Bin
v
v
v

8. More Right Hand Rule Practice
• Find the B Field in the following:
F F
V V
V XXXXXX
XXXXXX F
XXXXXX
XXXXXX