1. Electricity and Magnetism

2. Static Electricity
How are static charges produced and transferred?

3. Electric Charge There are only two types of charges: positive and negative. + → ← - ← + + →

4. How do atoms become charged?
Atoms normally have the same number of electrons and protons.
If an atom loses an electron, it now has more protons and is positive.
If an atom gains an electron, it now has more electrons and is negative.

5. Law of Conservation of Charge
Charges are not created or destroyed. They are simply transferred from one object to another.

6. + + - + Charges Two charges of the same type repel one another
Two charges of the opposite type attract one another - +
The two charges will experience a FORCE pushing them apart
or pulling them together

7. Methods of Charging
Friction – one object rubs against another and transfers electrons (ex. Rubbing balloon on hair)
Contact – charging an object by touching it to a charged object (ex. Pie pan becomes charged when it touches Styrofoam).
Induction – Charging a conductor by bringing a charged object near (ex. Ground underneath thundercloud)
Polarization – Charging an insulator by bringing a charged object near (ex.- picking up tissue paper with a comb)

8. Charging by Contact

9. Charging by Induction

10. Electrical Current
How can we compare and contrast series and parallel circuits?
What is the relationship between voltage, current, and resistance?

11. How are current, voltage, and resistance in a circuit related?
These are the 3 variables in any electrical circuit.
♦ Voltage ♦ Current ♦ Resistance

12. Voltage
Voltage is the measure of energy given to the charge moving in a circuit.
The greater the voltage, the greater the force or “pressure” that moves the charge through the circuit.
Voltage is sometimes referred to as “potential difference” and is measured in volts.

13. Current
Current is the flow of electrons from one place to another. It is measured in amperes (amps). Current is kinetic energy.

14. Difference between volts and amps
Amps measure how much water comes out of a hose.
Volts measure how hard the water comes out of a hose.

15. Resistance
The opposition to the flow of an electric current, producing heat.
The greater the resistance, the less current gets through.
Good conductors have low resistance.
Measured in ohms.

16. What influences resistance in a circuit?
Material of wire – aluminum and copper have low resistance.
Thickness – the thicker the wire the lower the resistance.
Length – shorter wire has lower resistance.
Temperature – lower temperature has lower resistance.

17. Conductors and Insulators
Conductors – material through which electric current flows easily.
Insulators – materials through which electric current cannot move easily.

18. Examples of Conductors and Insulators
Metal
Water
Insulators:
Styrofoam
Rubber
Plastic
Paper
Pure water will not conduct electric current !!!

19. So…How are current, voltage, and resistance in a circuit related?
They are related by OHM'S LAW
V = I x R
V = Voltage I = Current R = Resistance

20. Practice with Ohm’s Law
Volts
Amps ?
100 25
150 10 30 15 9 5 6 48

22. Electric Circuits
How are electrical components connected in a simple circuit?

23. 2 kinds of Simple Circuits
Series Circuit
Parallel Circuit

24. Series Circuit
The components are lined up along one path. If the circuit is broken, all components turn off.

26. Series circuit one continuous path for current to flow+ _
one continuous path for current to flow
if the circuit is broken all components go
off. I
I = I1 = I2 = I3 R1 V
V = V1 + V2 + V3 R2 R3
Re = R1 + R2 + R3

27. SERIES CIRCUITS Summary
The components are connected end-to-end, one after the other.
They make a simple loop for the current to flow round.
If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.

28. Parallel Circuit
There are several branching paths to the components. If the circuit is broken at any one branch, only the components on that branch will turn off.

30. Parallel circuits multiple paths for current to flow+ _
multiple paths for current to flow
two elements have two common points of connection I
I = I1 + I2 + I3
V = V1 = V2 = V3 V R1 R2 R3
1/Re = 1/R1 + 1/R2 + 1/R3

31. PARALLEL CIRCUITS Summary
The components are connected side by side.
The current has a choice of routes.
If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.

32. Equivalent Resistance
Series Circuit
Series Circuit

33. Look at the first set of resistors.
6 + 6 = 12 ohm.

34. Equivalent Resistance
Parallel Circuit
Parallel Circuit

35. Look at the first set of resistors
Look at the first set of resistors. You take the reciprocal sum of the resistances to get the total resistance. ¼ + ¼ = 2/4: If you take the reciprocal of 2/4, you get 4/2, which is 2.

36. Equivalent Resistance Practice
Determine the equivalent resistance of a series circuit with the following resistances.
4 Ω 6Ω 8Ω and 2Ω
Determine the equivalent resistance of a parallel circuit with the following resistances.
2 Ω 2Ω 4Ω and 8Ω

37. Direct Current
Direct current or DC electricity is the continuous movement of electrons from an area of negative (−) charges to an area of positive (+) charges through a conducting material such as a metal wire.

38. Alternating Current . Used in homes and businesses
Electric current that repeatedly reverses direction. Electrons move in one direction and then the other about fixed positions.

39. How do wet cells work?

41. Electromagnetic Induction
Magnetism
and
Electromagnetic Induction

42. How are Magnetic Fields Produced?
A magnetic field is a field of force produced by moving electric charges, by electric fields that vary in time, and by the 'intrinsic' magnetic field of elementary particles associated with the spin of the particle.

43. Magnetism

44. A Very Attractive Topic

45. What is Magnetism?
Magnetism is the properties and interactions of magnet forces
Magnets produce magnetic forces and have magnetic field lines

46. Magnetic Poles
The pole is the area on a magnet where its force is the greatest.
Each magnet has two poles.
If a magnet is broken in half, each piece becomes a magnet with two poles.
If you suspend a bar magnet, the north pole points north.

47. Magnets have two ends or poles, north and south
Magnets have two ends or poles, north and south. At the poles of a magnet, the magnetic field lines are closer together.
Unlike poles of magnets attract each other and like poles of magnets repel.

48. Magnetic Poles For every North, there is a South!
Like poles repel and opposite poles attract.
Unlike electric charges, magnetic poles cannot be separated!

49. Magnetic Forces
Magnets exert a force of attraction between opposite poles and a force of repulsion between like poles.
The force is smaller when magnets are farther apart and larger when they are closer.

50. Magnetic Fields
The space around a magnet, in which a magnetic force is exerted is a magnetic field.
Field lines spread out from the north pole of the magnet and return to the south pole of the magnet.
Magnetic field strength is greatest at the poles.

51. Magnetic Fields
A magnetic field is produced by the motion of an electric charge.

52. Magnetic Fields
A compass needle will align itself with a magnetic field.
A magnetic field is produced by the motion of an electric charge.

53. Tracing Field Lines with a Compass

54. Tracing Field Lines with a Compass

55. Tracing Field Lines with a Compass
If we place several compasses anywhere in the magnetic field, its poles will tend to line up with the magnetic field.

56. Magnetic Domains
The magnetic fields of individual iron atoms are so strong that interactions with adjacent iron atoms cause large clusters of atoms to line up with one another. These clusters are called domains and each is perfectly magnetized and contains billions of atoms.

57. Magnetic Domains
Electromagnet

58. A Magnetic Field around a Wire
When current flows in a wire, a magnetic field forms around the wire. The direction of the magnetic field depends on the direction of the electric current in the wire.

59. Ways to Strengthen the Magnetic Field around a Wire
Coil Wire (make a solenoid)
Increase Current
Insert an Iron Core (make an electromagnet)

60. Electric Currents and Magnetic Fields
When electric current flows through a conductor a magnetic field is produced.

61. Earth’s Magnetic Field
The earth’s magnetic field is thought to be caused by moving currents in the earth’s core.
Auroras occur when charged particles from the sun get trapped in the van Allen belts and interact with the earth’s atmosphere.

62. Earth’s Magnetic Poles
Poles can be thought of as “north-seeking” and “south-seeking”. The north pole of a compass points to the geographic north. Since unlike poles attract, we can conclude that the geographic North Pole corresponds to the magnetic south pole of the earth.

63. Earth’s Magnetic Field

64. The Northern Lights…

73. The Southern Lights…

81. The End

82. The End !