1. Electricity and Magnetism
12/27/2007

2. REMEMBER THE PARTS OF AN ATOM??
Protons ( positive)
Neutrons ( neutral )
Electrons ( negative )
The force that holds a nucleus together is called an ELECTROMAGNETIC or STRONG FORCE

3. Normally…..
Normally the electrons and protons are equal to BALANCE the charges in the atom.
IF atom gains or loses electrons to become stable than it is CHARGED.
Gaining electrons makes an atom NEGATIVELY charged and LOSING electrons makes them POSITIVELY CHARGED.

5. How can we charge an atom?
AGAIN..Atoms can be charged by GAINING or LOSING electrons.
Remember ( forming ions occurs when atoms are gained or lost through chemical reactions)
THERE ARE OTHER WAYS TO GAIN OR LOSE ELECTRONS.

6. What are electrical CHARGES?
These occur when a charge is GAINED or LOST through TRANSFERRING ELECTRONS by
Friction – rubbing
Induction – bringing a charge object near an neutral object
Conduction – flowing through direct contact ( this is sometimes called transfer through CONTACT)

7. Unlike the situation where like dissolves like …
This is because the surrounded by an ELECTRICAL FIELD

8. What is static electricity?
This occurs can occur when friction transfers ELECTRONS from one object to ANOTHER.
The shock you feel occurs when the electrons are transferred from your hand to the KNOB.

9. Examples:
1. Like the shoes rubbing against the carpet. Electrons are transferred from the carpet to the shoes.
2. Rubbing a balloon on your shirt…electrons are transferred from your shirt to the balloon.
3. When you remove clothes from the clothes dryer some have gained electrons and some have lost them. They will stick together.

10. More examples
. Electrons move from your hair to the hat. Now each of the hairs has the same positive charge.The farthest they can get is to stand up and away from all the other hairs.

11. How does lightning occur?
Positively charged particles are moved to the top of the cloud and negatively charged particles are moved to the bottom of the cloud.
                                                                                                     

12. What is a A Van der Graaf ?

13. How does an electroscope work?
An ELECTROSCOPE is device used to detect a static charge.
An positive of negative charge on both leaves will cause the leaves to REPEL and move away from each other.

14. Which way will the balls move and why

15. What is the difference between static electricity and current electricity?
STATIC electricity is stationary or collects on the surface of an object,
CURRENT electricity flows THROUGH A CONDUCTOR

17. How are good conductors different from poor conductors?
Good conductors – metals especially copper which is commonly used in electrical wires.
Poor conductors / resistors – they slow but do not stop the flow of electrons.
Insulators – they STOP electrical flow.

18. How are voltage current and resistance related?
voltage (electric potential) is flowing through the wires of the circuit. (V). It is similar to the buildup of water in the previous picture.
THE CURRENT is measured in Amperes (A).
Resistance (R) is the opposition to the flow of an electric current, causing the electrical energy to be converted to thermal energy or light (measured in ohms) (Ω).
V= I R

19. Understanding resistance …..

20. Ohm’s Law calculations…

21. How a lightbulb works…
The metal which makes up a light bulb filament or stovetop eye has a high electrical resistance. This causes light and heat to be given off.

22. How does a battery work?
Batteries are composed of a chemical substance which can generate voltage which can be used in a circuit.

23. What are the Parts of an electrical circuit?
voltage source ( BATTERY) , a wire conductor, and one or more devices which use the electrical energy (ie lightbulb) .
What is a series circuit?
A series circuit is one which provides a single pathway for the current to flow. If the circuit breaks, all devices using the circuit will fail.

24. What is a parallel circuit?
A parallel circuit has multiple pathways for the current to flow. If the circuit is broken the current may pass through other pathways and other devices will continue to work.

25. What is the difference between an open circuit and a closed circuit?
A closed circuit is one in which the pathway of the electrical current is complete and unbroken.
An open circuit is one in which the pathway of the electrical current is broken.

26. How is Electrical Power calculated?
Electrical Power is the product of the current (I) and the voltage (v)
The unit for electrical power is the same as that for mechanical power in the previous module – the watt (W)
Example Problem: How much power is used in a circuit which is 110 volts and has a current of 1.36 amps?
P = I V

27. What is magnetism?
Magnetism is the properties and interactions of magnets
The Magnets produce magnetic forces and have magnetic field lines

28. Magnets have two poles…Unlike poles attract and like poles repel….

29. What are magnetic domains?
Magnetic substances like iron, cobalt, and nickel are composed of small areas where the groups of atoms are aligned like the poles of a magnet.

30. Electricity and Magnetism – how are they related?
When an electric current passes through a wire a magnetic field is formed.

31. The MORE COILS THE GREATER STRENGTH
What is an electromagnet?
When an electric current is passed through a coil of wire wrapped around a metal core, a very strong magnetic field is produced. This is called an electromagnet.
The MORE COILS THE GREATER STRENGTH

32. What is a Galvanometer?
A galvanometer is an electromagnet that interacts with a permanent magnet.
The greater the current passing through the wires, the stronger the galvanometer interacts with the permanent magnet.

33. What are electric motors?
An electric motor is a device which changes electrical energy into mechanical energy.

34. How does an electric motor work?

36. What is electromagnetic induction?
Moving a loop of wire through a magnetic field produces an electric current. This is electromagnetic induction.

38. Direct current versus alternating current
Direct current is electrical current which comes from a battery which supplies a constant flow of electricity in one direction.
Alternating current is electrical current which comes from a generator. As the electromagnet is rotated in the permanent magnet the direction of the current alternates once for every revolution.

39. What happens to the water from a garden hose when the water is turned on, and there is a hole in the hose? What does this have to do with electricity?

40. What is electricity?

44. Between a longitudinal and transverse waves
What is the difference
Between a longitudinal and transverse waves

45. Please Write down all the equations for electricity!

46. Project!
You will create a diagram of the electricity in one of the rooms in your home!
Please make sure you use correct symbols.
You will also need to calculate the electricity in one of your rooms.

48. a) Draw a circuit with one bulb and one cell as you would see it in ‘real life’.
b) Now draw the same circuit, but use symbols to represent the different components. 

50. WARM UP: If my computer has a resistance of 22 ohms draws a current of 5.0 Amperes, what is the power of my computer?

51. Current(I) (in amps) = Voltage (V) (in volts) I = V or V=I x R
Resistance(R) (in ohms) R
Power(Watts) = Voltage(volts) X Current(amperes)

52. What current flows through a hair dryer plugged into a 110 Volt circuit if it has a resistance of 25 ohms?

53. A 12 Volt car battery pushes charge through the headlight circuit resistance of 10 ohms. How much power is being used?

54. A heater in a house uses 1500 Watts of power
A heater in a house uses 1500 Watts of power. If the circuit is 110 Volts, what is the current through the heater?