1	Electricity and Magnetism Physical Science Lancaster High School Mr. Hayhurst
2	Electric Charge and Force 1. Static electricity is a part of life. Name at least five examples of static electricity that occur in your home. 2. Fabric softeners are commonly used today because they eliminate static cling. Explain why clothes in the dryer get static cling.
3	Electric Charge and Force 3. Why can walking across a carpeted room be a shocking experience? 4. Magnets have both north and south poles. While like poles repel each other, opposite poles attract each other. Explain the parallelism between magnetism and electric charge.
4	Electricity and Magnetism Electromagnetic energy has to do with charges and electron/proton balances. Electrical energy is the movement of a stream of electrons through a substance. Electricity can cause a magnetic field that can cause electrical currents. Can exist in both P.E. or K.E.
5	Static Electricity Static electricity is a result of electric charges that accumulate on an object. electrons are charged negatively protons are charged positively When electrons are pulled off of an atom the result is the atom becomes charged positive.
6	Static Electricity If many electrons are forced off of a substance that substance becomes charged positively. Positive charge is the electric charge of an object that has lost some of its electrons. the object wants to gain electrons. The negative electrons need to attach themselves to another atom.
7	Static Electricity A negative charge is the charge of an object that has an excess of electrons. the object wants to lose electrons The two atoms are attracted to each other because of static electricity. If the electron makes the jump back both atoms will again be neutral.
8	Static Electricity Neutral describes an object in which the number of electrons equals the number of protons. If there are many electrons that make the jump there is sometimes a spark.
9	Homework Activity (The activity corresponding to this datasheet begins on page 434 of the textbook.) 1. Rub two air-filled balloons vigorously on a piece of wool. 2. Hold your balloons near each other. 3. Now try to attach one balloon to the wall. 4. Turn on a faucet, and hold a balloon near the stream of tap water. 5. Explain what happens to the charges in the balloons, wool, water, and wall.
10	Current Electricity Current electricity is the continuous flow of electrons from one place to another. The flow of electrons through a substance is called current. It can be measured in volts. Volts are a measure of the amount of work done in moving electrons between two points in an electric circuit. can be thought of as the “push” is equal to current times resistance Þ V = IR
11	Current Current is measured in amperes (amps). Amperes are a measure of the number of electrons moving past a point in an electric circuit in one second. can be thought of as the “flow” are represented by I in the volt equation.
12	Resistance Resistance is all of the conditions that limit the flow of electrons in an electric circuit. Resistance is measured in ohms. Ohms are a measure of the amount of resistance in an electric circuit. represented by R in the volt equation. Volts, amps and ohms are related as follows; AKA Ohm’s Law Volts = amps x ohms
13	Resistance 1. A battery-operated CD player uses 12 V from the wall socket and draws a current of 2.5 A. Calculate the resistance of the CD player. 2. A light bulb has a resistance of 12 W. It is attached to a battery that has a voltage of 24 V. Calculate the current in the light bulb.
14	Circuits A circuit is a closed path through which electrons can flow. In order to keep electrons flowing through a circuit there must be a device that maintains a potential difference. Such as: a battery a generator
15	Circuit Diagram Circuits are diagramed with symbols to represent the different components of a circuit. Light Bulb Switch Connecting Wire
16	Activities Build the following circuit and test it. Switches are simply breaks in a circuit. When a circuit is broken, the circuit is said to be open. In an open circuit, electrons cannot flow and return to the positive pole of the battery. How do you think you might create a closed circuit?
17	Activities Using the circuit you have created, insert between A and B different types of materials. Try these: Does the bulb light up? Popsicle Stick paper clip eraser staple string Try other materials and complete the chart.
18	Series Circuit In a series circuit the electricity has only one path it can travel along. When any part of the circuit is disconnected, no current can flow through the circuit. This is called an open circuit electrons require a closed path or they won’t move at all.
19	Series Circuit Here is a series circuit diagram:
20	Parallel Circuit Parallel circuits contain separate branches for current to move through. More current moves through the paths of lowest resistance. All branches connect the same two points of the circuit so the potential difference is the same in each branch. When one branch of the circuit is opened current continues to flow through the other branches.
21	Parallel Circuit Here is a parallel circuit diagram:
22	Circuits 1. Inexpensive electrical power is essential. List at least ten electrical devices that you have used today. 2. In some strings of Christmas lights, none of the lights work if one light is burned out. What is a possible explanation for this? 3. A big feast is being prepared for several people in a home. The cooks are using a turkey roaster, the oven, an electric mixer, the blender, and the toaster. Every light is on and so is the refrigerator. All at once the power in the kitchen goes out. What is an explanation for this, and how can it be corrected?
23	AC~DC There are two types of electricity. AC or Alternating Current DC or Direct Current
24	Alternating Current moving a magnet near a conductor produces a current in that conductor produced by a generator or alternator as a magnet changes poles when spinning, electrons change their direction of travel, thus the term alternating
25	Alternating Current Current is produced when there is motion between the magnet and the coil of wire. It does not matter which moves, the magnet or the coil. This process is called electromagnetic induction. The current produced in this way is called induced current. This method is used by power plants to produce AC that is used in homes, schools and factories.
26	Direct Current produced by an electric cell (battery) electric cell has two reactions in which chemical energy is changed into electrical energy one that produces electrons one that requires electrons
27	Direct Current electrons flow in one direction, from negative to positive negative terminal is called an anode positive terminal is called a cathode
28	Electric Cells There are two types of electric cells, wet cells and dry cells. Wet cells use a liquid electrolyte (usually an acid) and dry cells use a paste as an electrolyte. An electric cell is only good as long as the reaction can take place. When the reaction is finished the cell is “dead.”
29	Electric Cells Batteries can be hooked up in series or in parallel. If they are hooked up in series then the voltage of each battery is added together Advantage: more power If they are hooked up in parallel then the voltage remains the same. Advantage: more longevity
30	Electric Cells Some electric cells can be recharged by using another voltage source and reversing the flow of electrons and resetting the chemical reaction. Examples of rechargeable cells are: Nickel Cadmium Batteries Nickel Metal Hydride Batteries (good for digital cameras)
31	Circuit Boards Build a circuit board which connects two light bulbs in series with one switch. Build a circuit board which connects two light bulbs in parallel with one switch. Obtain materials from your teacher.
32	Electrical Current 1. Dry cell batteries are a source of mobile electrical power. Name five devices that use dry cell batteries. 2. Give reasons why copper is normally used to wire a home for electricity. 3. Why is it important to unplug a device by pulling the plug instead of by yanking it out of the socket by pulling on the electrical cord? 4. Why are electrical appliances, such as razors, hair dryers, and curling irons, not to be used in the bathtub or shower?
33	Magnetism Magnetism is a property of matter in which there is a force of attraction or repulsion between like or unlike poles. The magnetic forces are strongest near the ends, or magnetic poles Like poles repel opposite poles attract The magnetic force decreases as the distance between them is increased.
34	Magnetic Fields The magnetic field is the area around the magnet where magnetic forces act. Electrons in the atoms of most materials exist in pairs and spin in opposite directions. Each spinning electron causes a magnetic field to form around it with a direction that depends on the direction of spin.
35	Magnetic Fields So, the magnetic field of one electron is cancelled by the magnetic field of the other. In Iron, Cobalt and Nickel the electrons are not paired, so the electrons’ magnetic fields do not cancel. Each atom of these elements acts like a very small magnet.
36	Magnetic Domains The magnetic field created by each iron atom exerts force on the other atoms, causing groups of atoms to align their magnetic poles so that all like poles are facing the same direction. These groups of atoms are called magnetic domains. Even the smallest pieces of a magnet have a north and a south pole.
37	Magnetic Domains Magnetic Field around a single Magnet
38	Magnetic Domains Magnetic Field generated by like poles:
39	Magnetic Domains Magnetic Field generated by opposite poles:
40	Electricity and Magnetism