1. The shadow of electricity
Magnetism
The shadow of electricity

2. Objectives
Identify the direction and distance dependence of the force between magnetic poles.

3. Magnetic fields

4. Magnets Attract and Repel
Magnets apply forces to each other.
Opposite poles attract, like poles repel.

5. Poll Question The magnitude of the force between magnetic poles
is the same at all distances.
becomes stronger as the poles come closer.
becomes weaker as the poles come closer.

6. Magnetic Field Lines Conventions as with electric field lines.
direction is direction of force on a north pole
strong field where lines are close together
Field lines point from North to South pole.

7. Board Work
Sketch the pattern of magnetic field lines for two dipole magnets positioned as N S N S

8. Naming the poles
N = north-seeking
Earth’s north pole is a south pole!

9. Poll Question
What happens if you break a magnet between its north and south poles?
You make two smaller magnets, each with a north and south pole.
One piece will be a north pole and one piece will be a south pole.
One piece is a magnet and the other is not.
None of these.

10. Do Magnetic Poles Exist?
North or south poles have never been isolated!
Source: Hewitt, Fig. 24.7
Magnetic “monopoles” probably do not exist.

11. Reading for Next Time Magnets and charges Main ideas
How magnetic fields act on electric charges