1. Magnetism and Electromagnetism

2. Magnetism day 1

3. 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)

4. 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.

7. 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

8. 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)

9. 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)

10. 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

11. Moving charged particles

13. Right Hand Rule #1
*Thumb in direction of current
*Fingers show how the magnetic field wraps around the wire

14. What does the magnetic field look like around this wire?

15. Right hand rule #2 Force on a moving charge
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

16. 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 +
Note speed never changes; this causes the particle to curl. + + v FB + +
Force is always  to v + + v

17. What will be the direction of the magnetic force on this proton?

18. What will be the direction of the magnetic force on this proton?

19. 2nd Right hand rule

20. 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?

21. Magnetism day 2

22. 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

23. 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)

25. Three every day Items that use electromagnetic induction
Electric Motors
Electric Generators
Electric Transformers

26. Electric motors Electromagnet in a magnetic field will rotate
electrical energy used to produce mechanical energy

27. Electromagnet
making an electromagnet—wrap a current carrying wire around iron core and it will set up a north and south pole

28. Electric motors
Electromagnet in a magnetic field will rotate (kinetic energy)
electrical energy is used to produce mechanical energy

29. Electric motor Commutator ring
Commutator allows the current in the electromagnet to switch directions so the motor shaft spins continuously

30. 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

31. 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.

32. Putting it all together…
Spinning turbines and generators are inside this power plant

33. Electromagnet
making an electromagnet—wrap a current carrying wire around iron core and it will set up a north and south pole