1. Chapter 22 Magnetism and its Uses

2. Objects 22.1 Describe the properties of magnets
22.1 Define the region of force around a magnets
22.1 Model magnetic behavior using domains

3. Objects 22.2 Explain the magnetic effects of a current in a wire
22.2 Compare and contrast ammeters and voltmeters
22.2 Describe the function of an electric motor.

4. Objects
22.3 Describe how a generator produces an electric current using electromagnetic induction
22.3 Distinguish between alternating and direct current
22.3 Explain how a transformer can step up or step down the voltage of an alternate current

5. Objectives 22.4 Describe the characteristics of superconductors
22.4 Consider various applications of superconductivity

6. Key Words Magnetism Magnetic Pole Magnetic Field
Magnetic Domain Electromagnet Ammeter
Voltmeter Electric Motor
Electromagnetic Induction
Generator Direct Current Alternating current
Transformer Solenoid

7. Magnetism
Magnetism is a property of matter in which there is a force of attraction or repulsion between unlike or like poles
One positive end, one negative end
Most metals area actually NOT magnetic
Iron, Cobalt and Nickel metals which are actually magnetic
Other metals can be temporary magnets

8. Opposites Attract

9. The Earth
Earth is a big magnet. The actual location of the magnetic poles change every year by about 40 miles
Earth’s magnetic poles change yearly

10. Magnetic Declination
Your compass points to the magnetic pole, not to the true north pole
As you approach the poles, you have to add/subtract degrees to go the right direction
Compass is wrong close to poles

11. The north arrow on the compass rose (the large N) is pointed towards the place on the horizon directly beneath the North Star! That is, towards true north!
And the needle (of course) points towards magnetic north! So the magnetic declination for this locality is 45 degrees west

12. Magnetic Domains
Groups of atoms with aligned magnetic poles are called

13. Magnetic Fields Points towards the South Pole
So, South must be Negative end
Since magnetic fields point towards the negative charge
Magnetic Pole: End of magnet, strongest magnetic field
Earth’s North pole
Is the south magnet

14. Electromagnet
A type of magnet created by current passing through a coil
Electromagnetic Induction: The process by which moving a wire through a magnetic field produces a current

15. Solenoid: Coils wrapped around with a current moving through
Solenoid: Coils wrapped around with a current moving through. Used in MRI’s

16. Thumb points towards the North End

17. Magnetic Field Force
The current causes the magnetic field
The magnetic field in turns pushes on the wire
Electric Motor: Turns electrical energy into mechanical energy

18. Reading Current and Voltage
Voltmeter: Determines the voltage drop across a resistor
Ammeters: Determine the current through a wire
Determined by deflection caused by the magnetic field

19. Generator
Produces electric current by rotating wires in a magnetic field
See simulator

22. Direct Current
DC = Direct Current. The flow (current) of electrons is in one direction
Like a river runs only down hill, direct current only flows one way.
Batteries provide this type of current

23. Alternating Current
AC = Alternating Current Electrons flow back and forth. The electrons are pushed one way, then pushed the other way.
The electrons stay in roughly the same area, just going back and forth. Our outlets provide this, alternating current.

24. Alternating Current
In the USA, there are three wires that transmit the flow of energy.
Two are at + or – 120 Volts (180 degrees out of phase)
One is at 0 Volts
The US has adopted a frequency of 60 Hz
The polarity (direction of electrons) changes 120 times per second
Actual voltage of peaks are + and – 170 volts

25. Transformers Step Up or Step Down the Voltage
A transformer is just a piece of iron with a pair of wires coiled around it - one with many more turns in the coil than the other.
The coils of wire are not physically connected. The iron core is immersed in an insulating oil bath which does not conduct electricity well.
Step Up or Step Down the Voltage

26. Transformers