1. Electricity & Magnetism

2. Magnets are Cool Watch this video until 0:35.
What happens to the sliding magnet when the system is turned upside down?
It is launched at high speed
It falls at 9.81 m/s2
It does not move
It falls toward the other magnets

3. Magnetic Fields
We say that magnets are surrounded by a magnetic field of force exiting the magnet at one end, and re-entering at the other end.
We can sense these fields with ferromagnetic materials (e.g. iron filings) or other magnets (compasses).
Watch This Video

4. Magnetic Fields
The shape and direction of the field around a magnet is determined using a compass.

5. Magnetic Fields

6. Magnetic Field Lines

7. Magnetic Field Lines Properties of magnetic field lines:
Outside the magnet, point from north to south.
Inside the magnet, point from south to north.
Never cross.
Are denser when the magnetic field is stronger (i.e. the more closely spaced the lines, the greater the force.)

8. Magnetic Field Around the Earth

9. Magnetic Field Lines

10. Magnetic Force
Law of Magnetic Forces:
1. Opposite poles attract

11. Magnetic Force
Law of Magnetic Forces:
2. Similar poles repel

12. Magnetic Force Law of Magnetic Forces:
3. Force varies inversely as the square of the distance between the poles.
Distance
Force
1.0 m
100 N
2.0 m
5.0 m
× 2
× ?

13. Magnetic Field Lines Magnetic field around a bar magnet
Magnetic field between a pair of opposite poles

14. Magnetic Domains What happens if you break a magnet in half?
Each piece will always have a north-seeking pole and a south-seeking pole.
For this reason, magnets are called dipoles.
In contrast, electric charges are known as monopoles.

15. Magnetism What happens to permanent magnets when they are heated?
Check This Out
Nothing
They stop being magnetic
They explode

16. Magnetic Field Lines

17. Electricity vs. Magnetism
To each statement about electric charges, write a corresponding statement about magnets.
There are positive and negative electric charges.
Electric charge is due to the excess or deficit of electrons.
Electrically charged objects can attract or repel other charged objects and neutral objects.
Electric charges don’t require contact in order to exert a force.

18. Homework!
Pg. 552 #5ab, 6abd
Read and take notes on “Magnetic Fields at Work” Pg