Magnetism

1
Chapter 19

• Magnetism

2
Magnetism

• Magnetite and Magnesia
• Attraction between metallic rocks
• Ferromagneticmaterials with strong magnetic
  properties
• Iron, Nickel, Cobalt, very few others
• Permanent magnetsnaturally maintain a magnetic
  field
• Electromagnetsmagnetism caused by forced
  electrical current
• can be turned on and off

3
Magnetism

• Polespoints on a magnet where magnetic effect is
  strongest
• North polewill move to face geographic north on
  Earth
• South polewill move to face geographic south on
  Earth
• Poles always occur in pairs
• No pole exists alone
• Break a magnet in half, each half develops two
  poles

4
Magnetism

• Opposite poles attract
• Like poles repel
• Earths magnetic poles are opposite the
  geographic poles
• North geographic corresponds to South magnetic

5
Maglev trains
6
Magnetism

• Electromagnetismstudy of electrically charged
  particles and magnetic fields
• Magnetism is caused by moving electric charges
• Magnetism only effects moving electric charges
• No effect on stationary charge

7
Magnetic Fields
8
Magnetism

• Electric charge moving through a magnetic field
• Right hand rule (positive charge)
• Thumbpoint in direction of charge movement
• Fingerspoint in direction of magnetic field
  lines
• Palmdirection of force on the moving charge
• smacks the charge
• Left hand rule (negative charge)
• Same rules, just use the left hand

9
Magnetism

• F Force on electric charge
• Q charge
• v velocity of charged particle
• B magnitude of magnetic field
• Units of Tesla (T)
• Alternate unit, Gauss (1G 10-4 T)
• ? angle between velocity vector and magnetic
  field lines

10
Moving in circles
Fermi National Accelerator Lab Chicago, IL
Typical particle trace
11
Force on a current carrying wire

• F force
• I current
• L length of wire in magnetic field
• B magnetic field strength
• ? angle between velocity vector and magnetic
  field lines

12
Electromagnetism

• Magnetic field lines form concentric circles
  around straight, current carrying wires
• B magnetic field strength
• I current
• d distance away from the wire
• µ0 1.26 x 10-6 Tm/A 4? x 10-7 Tm/A

13
Electromagnetism

• Current carrying loops
• B magnetic field strength (at center of loop)
• I current
• r radius of the loop
• N number of loops

14
Electromagnetism

• Solenoidslots of loops stacked together
• Generally longer than the diameter of the loops
• B magnetic field strength at the center of the
  solenoid
• L length of solenoid
• I current
• N number of loops

15
Galvanometers

• Loop of wire inside a magnetic field
• Place a needle (pointer) on the loop
• Spring to resist movement of loop
• Movement of pointer is directly related to the
  current in the loop
• Ammeters, voltmeters, speedometers, anything with
  a needle

16
Motors

• Loop of wire inside a magnetic field
• Converts electrical energy into mechanical energy
• Supply current (moving charges)
• Resulting Magnetic force turns the loop of wire

17
Generators

• Loop of wire inside a magnetic field
• Converts mechanical energy into electrical energy
• Move charges by turning the loop
• Resulting force pushes charges throughout the
  wire, creating current

18
Power Generation by fuel type
19
Generating Capacity by fuel type