1. Electricity and Electromagnetism Electricity Magnetism Electromagnetism

2. Electricity Electricity – the flow of electrons Static electricity – buildup of electrical charges Electric current – movement of electrons from one place to another Ampere – the unit used to describe how much electric current flows through a wire.

3. Circuit – a path for electric current Closed circuit A complete, unbroken path for electric current Open circuit An incomplete or broken path for electric current

4. Schematic Diagram Schematic diagram – a diagram that uses symbols to show the parts of a circuit

5. Schematic Diagram

6. Conductors and Insulators Conductor – material through which electricity passes easily –Examples, metals such as copper, gold, aluminum and silver; solutions that contain electrolytes Insulator – material through which electricity does not pass easily –Examples, glass, rubber, wood, and plastic

7. Resistance Resistance – measure of how easily electric current will flow through a material Ohm – the unit used to measure resistance Resistance depends on: –The material the wire is made of –The length of the wire –The thickness of the wire The higher the resistance of the current flow, the greater the heat produced by the circuit.

8. Sources of Electric Current Electromotive force – the push that keeps the current flowing in a circuit Volt – the metric unit used to measure electromotive force that tells the amount of push Voltage – the energy that a power source gives to electrons in a circuit When the voltage is high, the electrons have more energy available to do work.

9. Batteries Battery – common source of voltage Dry-cell battery – electric power source with a dry or paste-like center Terminal – points where electrons leave or enter a battery The positive terminal (+) receives electrons from the negative terminal (-), which has an excess of electrons

10. Batteries Wet-cell battery – electric power source with a liquid center Made with sulfuric acid and a series of lead plates. A chemical reaction takes place between the acid and the plates, causing the electrons to move from one plate to another.

11. Batteries

12. Current Direct current (DC) – current that flows in one direction –Not the most common type of current. Found in batteries Alternating current (AC) – current that changes direction regularly –Electricity produced in homes. Machines called generators produce AC.

13. Ohm’s Law Power sources provide the push (voltage) to the current in a circuit. The rate at which the current flows can be measured in amperes. Ohm’s Law – current equals voltage divided by resistance Current = electromotive force/resistance I = V/R

14. Ohm’s Law What is the current of a circuit that has electromotive force of 15 V and a resistance of 3  ? I = V/R I = 15 V/3  I = 5 A

15. Ohm’s Law What is the electromotive force produced by a circuit with a current of 7 A and a resistance of 4  ? I = V/R 7 A = V/4  V = (7 A)(4  ) V = 28 V

16. Ohm’s Law What is the resistance of a circuit that has an electromotive force of 90 V and a current of 5 A? I = V/R 5 A = 90 V/R R = 90 V/5 A R = 18 

17. Circuits Series circuits – a circuit in which all current (electrons) flows through a single path Disadvantages – one light is unscrewed or burns out, all of the other lights will go out. The circuit becomes open and the electrons cannot flow. The current remains the same in a series circuit, no matter how many electrical devices are connected. Adding electrical devices to the series lowers the voltage through each device.

18. Circuits Batteries connected in a series circuit increase the voltage of the circuit. Add the voltages together to obtain the total voltage. Lights are brighter because batteries are connected in series circuits. Flashlights have batteries connected in series. Fuses or circuit breakers will break the flow of electrons, which may prevent fires.

19. Circuits Parallel circuits – a circuit in which there is more than one path for current If one bulb burns out, the rest remain on because the electrons have more than one pathway to move. When several bulbs are connected in parallel, they are the same brightness. However, the more electrical devices that are connected increases the current, which increases the heat.

20. Circuits Batteries in parallel circuits provide energy for a longer period of time. Batteries in parallel do not increase the voltage. It will not cause lights to be brighter.

22. Measuring Electricity Light bulbs have the amount of power they use stamped on them –100 W stands for 100 watts –50 W uses twice as much power as 25 W Electric power – the amount of electrical energy used in a certain amount of time Kilowatt-hour – a unit used to measure how much electric energy is used; it is 1,000 watts used in one hour

23. Magnets Magnet – an object that attracts certain kinds of metals, such as iron Many types of magnets are man-made, created by running an electrical current outside of a bar of metal Lodestone is a naturally occurring magnet Magnetic pole – the end of a magnet, where magnetic forces are greatest –Attract – to pull together –Repel – to push apart

24. Magnets Magnetic field – area around a magnet in which magnetic forces can act Lines of force – lines that show a magnetic field

25. Magnets Earth is a giant bar magnet. North magnetic pole and the south magnetic pole attract each other.

26. Magnetism Some atoms have north and south magnetic poles, but most substances do not. Therefore, certain substances are magnetic, while others are not. Materials that are not magnetic are wood, copper, plastic, rubber, gold, and glass. Also, magnets are not attracted to these substances.

27. Magnetism Substances that are magnets have their atoms arranged so that they line up with corresponding poles, north poles in one direction and south poles in another direction. Therefore, these substances are magnets. Substances that can be made into magnets are iron, nickel, and cobalt. Magnets are also attracted to these substances.

28. Magnetism To make a magnet, use another magnet and stroke it over a piece of iron. After four or five strokes, the iron will become magnetized. Even if the iron is cut in two pieces, both pieces will remain magnetized because the atoms are lined up with a north and south pole.

29. Magnetism Two ways to demagnetize a magnet. Heating the magnet will rearrange the atoms in a magnets so they are no longer lined up. Striking the metal with a hard blow will also rearrange the atoms in a magnet so they are no longer lined up.

30. Electromagnetism Electromagnetism – the relationship between magnetism and electricity Electromagnet – a temporary magnet made by passing a current through a wire wrapped around an iron core. The strength of the electromagnet depends on power sources with high voltage and the number of turns of wire around the core.

31. Electromagnetism

32. When current is supplied to the electromagnet, each pole is attracted to the opposite pole of the permanent magnet. This attraction causes the electromagnet to turn. The turning of the electromagnet causes the motor to turn. As the direction of the current changes, the electromagnet’s poles are reversed. This causes a spinning motion, which works the motor. Motors operate cars, refrigerators, electric toys, hair dryers, air conditioners, and kitchen appliances.

33. Electromagnetism Speakers, earphones, and telephones use electromagnets to change electric currents into sound waves Motor – device that converts electrical energy to mechanical energy –Permanent magnet cannot move –Electromagnet that is free to turn –Device that supplies alternating electric current to magnetize the magnet