1. Physical Science
Chapter’s 20 and 21

2. Think about it 
How are lighting and static cling on your clothes related?
Movement of Electric Charges!

3. What is an electric charge?
Electric charge- a property that causes subatomic particles (protons and electrons) to attract or repel each other

4. What creates a charge?
An excess or shortage of electrons produces a net electric charge.
Ex. Rubbing a balloon on your head. The balloon will become negatively charged and it will attract positively charged bits of paper.

6. How are charges attracted or repelled?
Positive and negative charges attract.
Like charges repel
Ex. Think about the north and south ends of a magnet

8. How do charges affect other charges that are close?
Electric charges affect other charges within their electric fields.
The strength of an electric field depends on the amount of charge that produces the field and on the distance from the charge.

10. Static electricity and charging
Static electricity is the study of the behavior of electric charges
Net charges can build up in several ways
Charge can be transferred by friction, by contact and by induction.

11. Electric Circuits
An electric circuit is a complex path through which a charge can flow
Circuit diagrams use symbols to represent parts of a circuit, including a source of electrical energy and devices that are run by the electrical energy
Ex. Wiring a house or a car

12. Lab Safety
Don’t attach the alligator clips to anything other than the battery or bulb
Don‘t lick the bulb or the battery- eww.
Be careful, the bulbs ARE glass, and if you squeeze them too tightly they will break…
It’s ok if something breaks or doesn’t work, just let me know and I will help you.
* Try a few times before you call me over.

14. Closed and Open Circuits
On a circuit diagram switches indicate where a circuit can be opened.
If a switch is open the circuit is not a complete loop and the current stops = OPEN CIRCUIT
If a switch is closed the circuit is complete and the charge can flow = CLOSED CIRCUIT

15. Series Circuit
In this type of circuit charge has only one path through which it can flow.
If one element stops functioning in a series circuit, none of the elements can operate.
Ex. Christmas lights

16. Parallel Circuit
A parallel circuit is an electric circuit with two or more paths through which charges can flow.
If one element stops functioning in a parallel circuit, the rest of the elements still can operate.

17. Conductors and Insulators
Conductor- material that charges can flow through easily
Insulator- material that charges can not flow through easily
Ex. Wires – inside is copper conductor, outside is rubber insulator

18. Resistance Opposition to the flow of charges
Resistance is measured in Ohms
Ex. Thick milkshake = thick straw : resistance is lower if you make a wire thicker. More electrons can flow through a thicker wire 
Resistance is affected by a materials thickness, length and temperature

19. What is a superconductor?
A material that has almost zero resistance when cooled to low temperatures.

20. Voltage Related to potential difference
Think about potential energy- a battery is a source of potential energy
Charges flow spontaneously from a higher to lower potential energy. (Think about gravity)
Potential difference is measured in joules per coulomb or VOLTS.
Potential difference is also called VOLTAGE!

22. Charging by Contact
Ex. A Van de Graaff generator- makes your hair stand on end!
Charge is transferred by contact.
When you touch the generator you acquire a charge large enough to make your hair stand on end!

24. Charging by Induction
Ex. Touching a doorknob after walking across carpet.
Use of an electroscope!!! Next slide 
You picked up extra electrons from the carpet-therefore your hand is negatively charged. Your electrons repel the electrons in the doorknob leaving it positively charged –OUCH!
Induction- a transfer of charge without contact between materials

26. What is static discharge?
Ex. The static shock from the last example! –OUCH!
Static discharge occurs when a pathway through which charges can move forms suddenly.
Ex. When you make contact with the doorknob your hand becomes the pathway!

27. Van Der Graaf Generator Demos
Should a person touch 200,000 volts?
Big Sparks Little Sparks
How Does a Van Der Graaf Work?

29. Electricity Review (To Be Turned-in )
Electricity Questions
1) What creates a charge?
2) How does charging by friction work? Explain.
3) Give an example of charging by contact.
4) How does charging by induction work? Explain.
5) Current is the flow of electricity- give the two types of current. How are they different?
6)What is resistance and how is it measured?
Circuit Questions
7) Draw a series circuit with 3 light bulbs.
8) Draw a parallel circuit with 4 light bulbs.
9) How are open and closed circuits different?

30. Bill Nye!!
Bill Nye- Electric Circuits

32. Electric Current A continuous flow of electric charge Measured in amps
Two types
AC – alternating current
DC – direct current

33. Direct current
Charge is flowing in one direction

34. Alternating current
Flow of electric charge that regularly reverses direction

35. Ohms Law V = voltage I = current R = resistance
V = I x R or I = V/R
V = voltage
I = current
R = resistance
What is the voltage if the resistance is 3 ohms and the current is 3 amps?
V = I x R  3 amps x 3 ohms = 9 volts

36. Ohm’s Law
Ohm's Law defines the relationships between (P) power, (V) voltage, (I) current, and (R) resistance.
One ohm is the resistance value through which one volt will maintain a current of one ampere. ( I ) Current is what flows on a wire or conductor like water flowing down a river. Current is measured in (A) amperes or amps.

37. Ohm’s Law
( V ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.

38. Ohm’s Law
( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms.

39. Calculating Power
( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.
Formula for Power:
Power = Volts x Current
P = V x I

41. Magnetism Law of Magnets- opposites attract, like repel
Pass around the magnets, hold both north ends together and then a north and a south end
Do you feel the magnetic force?
Keep these away from your cell phone!!

42. Magnetism Magnetic force- force one magnet exerts on another
Acts over a certain distance.
Slide the magnet close to the paper clip, notice how close it has to be in order for the clip to jump towards the magnet.

43. Magnetism Magnets have two poles
Magnetic fields are strongest around the poles
Watch the demo on the projector 

44. Magnetism
Magnetic Domain- area with a large # of atoms aligned in magnetic fields

45. Magnetism IF a material is magnetic the domains are aligned
IF a material is not magnetic then domains are not aligned
Add the drawing on the board into your notes

46. Magnetism Ways to break a magnet: Heat it Hit it Drop it
Why do you think this would cause a magnet to not be magnetic anymore?

47. Electricity and Magnetism
Both are part of electromagnetic force
Pass the magnetic over the compass, what happened? Why?

48. Three Parts of an Electromagnet
Coil, Core, Current
An electric current creates a magnetic field
A moving magnetic field induces an electric current

49. Important!
Electric Motors convert a moving electrial current into a magnetic field
Generators convert a moving magnetic field in an electric current
How to make an electromagnet- COIL, CORE , CURRENT
How to build a simple generator