What is Electricity? Lesson one

Static Electricity Static Electricity: an electrical charge that builds up on an object Most of the time, matter is electrically neutral. The same number of positive and negative charges The charges cancel each other out, so the matter has no electrical charge.

Static Electricity Think about your socks in the dryer Your socks rub up against a shirt. Some clothes gain the negative electric charges, and other clothes lose those negative charges (and they end up with a positive charge).

Static Electricity Objects with opposite charges attract each other So, the sock sticks to the shirt

Static Electricity On the other hand, items with the same charge (positive and positive, or negative and negative) repel Electricity stays in an object until something happens to remove it. Going back to the socks: When I remove the sock, I hear a crackle and see a spark as the extra negative charges move between the sweater and sock.

Current Electricity Current Electricity: A steady stream of charges This is the type of electricity we use for power. It is more easily controlled than other types of electricity. A power plant produces a flow of charges The plant sends the current along wires We use the electricity in our houses

Circuits Circuit: the path an electric current follows Like a circle, the circuit has no beginning or end. For any electrical machine to work, the circuit must be complete, or closed. Open Light bulb doesn t work Closed Light bulb works

Series Circuits Series Circuit: a circuit that has only one path for the current to flow

Parallel Circuit Parallel Circuit: a path that has more than one way an electric current can flow The current can travel through both bulbs and light them; however, if one is missing, it can still light the one bulb. The circuit is still closed.

Electrical Conductors On the inside of an electrical wire, there is a wire made of metal. Metal is a good conductor of electricity. A conductor is a material that lets electricity travel through it easily.

Electrical Insulators Why can we touch wires that have electricity running through them? On the outside of the wire, there is a protective plastic or rubber coating. Plastic and rubber are good insulators.

Switches A switch is a device that opens or closes a circuit. When the circuit is closed, two conductors touch, and electricity will flow through the circuit.

Switches When the switch is open, the circuit is open, and the electricity cannot flow all of the way through the circuit.

Let s Review What is a conductor? A material that lets electricity travel through it easily. What is an example of a conductor? Metal such as copper What is an electrical charge that builds up in an object? Static electricity (remember the socks)

Let s Review What is the name of a path that has only one way for the current to flow? Series circuit What is a stream of electrons moving through a copper wire called? Current electricity (the type of electricity we use to power our stuff)

Let s Review This diagram shows a circuit. When one light bulb is removed, the others stay lit. Is this a parallel circuit or a series circuit? Explain This is a parallel circuit, because there is more than one path for the electrons to follow.

Let s Review This figure shows a switch in an electrical circuit. Is the switch part of the circuit a series connection or a parallel connection? Explain The switch is wired in a series. At the place where the switch is, there is no other path for the current to follow.

Electricity & Magnetism Chapter 4 Lesson Two Pgs. 150-161

Magnets Magnets: an object that attracts iron and a few (not all) other metals Distance affects the strength of a magnet s attraction A small steel object that is close to a magnet moves toward it If the same object is farther away, it will not move toward the magnet

Magnets Barriers can interfere with a magnet s pull Too many papers under a magnet on a fridge Magnets can make some other objects magnetic. If you rub a needle over a magnet several times in the same direction, the needle will become magnetic enough to pick up other needles.

Magnetic Poles A magnet has two places at which its force is the strongest Each of these places is called a magnetic pole If you tie a string around the middle of a bar magnet and let it swing, one end will point north (north seeking pole, marked with an N)

Magnetic Poles Forces between magnetic poles act like forces between electric charges Opposite poles attract, and like poles repel

Magnetic Poles Magnets of every shape and N and S poles If you try to hold two round fridge magnets together, one way they will stick to each other and the other way they will repel each other Magnets even keep their poles if you change their shape. If I cut a big bar magnet into small bar magnets, each piece would be a magnet with both an N pole and an S pole

Magnetic Fields Magnetic field: the space around a magnet in which the force of the magnet acts If you put iron filings around a magnet, you will be able to see the shape of the magnet s field. The filings form circles that start and end at the poles, where the magnet s pull is the strongest.

Electromagnets An electromagnet is a temporary magnet It can be made with a battery, wire, and a nail An electric current produces a magnetic field around a wire (you can t see it, but it circles the wire) The field around a single wire is weak, but the field around many wires close together is strong When coils wrap around an iron core, such as a nail, the core becomes an electromagnet

Electromagnets It has a magnetic force only when an electric current moves through the wire

Generators A magnetic field can produce electricity If you move a coil of wire near a magnet, current electricity flows in the wire Generator: a device that produces an electric current

Generators Power plants in large cities use many huge generators to make electricity Most power plants burn coal, oil, or natural gas The fuel heats water until it turns to steam The steam s pressure turns a turbine (a machine that produces a spinning motion) The turbine spins a coil inside the field of a magnet to produce electricity The electricity is sent out along power lines

Electric Motors Electric motors change electrical energy into mechanical energy They use an electromagnet and a permanent magnet to move things Mixer, hand drill, CD player, car starter, fan

Other Uses of Magnets Magnets are used in computers, cd players, and magnetic recording devices (VCRs) They are also used in headphones, stereo speakers, and telephone receivers Doorbells and phones ring because of magnets The strip on the back of a credit card is a magnet

Let s Review What is an electromagnet? A temporary magnet A machine that produces electric current is known as a. Generator An object that attracts iron is a. Magnet I want to build a small electric generator. What two items must I have to make my generator? A coil of wire and a magnet

What are some sources of electricity? Lesson Three

Potential and Kinetic Energy You can t always see energy, but you know it s there. Anytime something gets warmer, gets cooler, or moves, energy is being changed from one form to another. Your body gets energy from food This energy keeps you alive and provides power for all you do The energy stored in the food is released in your body

Potential Energy Objects can also have energy because of their position or because of what is done to them. A roller coaster car at the top of a hill has energy A rubber band has energy when it is stretched

Potential and Kinetic Energy Potential Energy: energy due to an object s position or condition The faster an object moves, the more kinetic energy it has.

Hydroelectric Power Another good example of potential and kinetic energy is a waterfall. At the top of the waterfall, the water has potential energy Potential Kinetic When the water falls, it gains kinetic energy

That Dam Report People use dams to change the kinetic energy of falling water into electrical energy called hydroelectric power.

As water flows down from the reservoir, it turns the turbine. The turbine turns the generator, which produces an electric current.

Geothermal Power Heat from inside Earth is called geothermal energy. In some places, reservoirs of hot water lie 2 miles or more below Earth s surface. A deep well can reach the hot water. People can pump up the water and use it to heat buildings.

Geothermal Power Geothermal energy can be used to produce electricity. Most power plants burn coal, oil, or natural gas to produce heat to turn water to steam. The steam turns turbines and the turbines spin generators.

Inside a geothermal plant, heat from below ground is used to make steam that turns turbines.

Solar Power Solar energy is the energy of sunlight. Solar energy can heat buildings without any special equipment. The south side of a building gets more sunlight than the other sides.

Solar Power Solar energy can also be used to heat water. A flat solar panel on the roof stores water in clear tubes. The sun shines on the water and heats it. Then the hot water is pumped inside the building for people to use.

Solar Power Solar panels can also be used to produce electricity. The sun can be used to power yard lights, calculators, and even houses.

Let s Review Energy an object has because of its position or condition is known as. Potential energy The energy of motion is known as. Kinetic energy What kind of energy is also called energy of position? Potential energy

Let s Review John and his family visited a large dam, where they were told that the kinetic energy of falling water was changed to electrical energy. What kind of power did this dam produce? A. Chemical power B. Hydroelectric power C. Geothermal power D. Solar power

Let s Review Office, homes, and factories each use about the same amount of electricity. If you made a pie graph to compare the amounts used, what fraction of the graph would be labeled for each kind of user? Energy Use Office Homes Factories

How Do People Use Energy Resources? Lesson Four

Chemical Energy Electricity in an important form of energy. It s not the only form of energy we use. We use the energy stored in gasoline to move cars.

Chemical Energy Chemical energy is energy stored in the arrangement of particles of matter. Gasoline, which is made from oil, has chemical energy. Chemical energy can be changed into other forms of energy. Car engines burn gasoline to change its chemical energy into mechanical energy. Mechanical energy makes machine parts move.

Chemical Energy Makes Batteries Work Batteries contain stored chemical energy that can be changed to heat, light, sound, or mechanical energy. This radio works because a chemical change in its batteries produces an electric current.

Let s Review What is stored in the bonds that hold compounds together? Chemical bonds Take out your white boards. Draw a series circuit. Draw a parallel circuit.