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Electricity and Magnetism

Electricity and Magnetism. 5/23 Static Electricity Notes. IQ: Name the particles of an atom. Which particles can move around/leave the atom?. What is Electricity?. A form of energy caused by moving electrons. Charge: A buildup or shortage of electrons.

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Electricity and Magnetism

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  1. Electricity and Magnetism

  2. 5/23 Static Electricity Notes IQ: Name the particles of an atom. Which particles can move around/leave the atom?

  3. What is Electricity? • A form of energy caused by moving electrons.

  4. Charge: A buildup or shortage of electrons. • Gaining or losing e-s develops a neg. or pos. charge in an object. • Charges exert forces (push or pull) on each other. • Law of Electric Charges • Like (same) charges REPEL • Opposite charges ATTRACT

  5. Most objects are electrically neutral.

  6. Static Electricity

  7. When you rub two substances together you do work and thus you add energy. • This removes electrons from one substance and adds it to the other. • Static electricity is the buildup of a charge on an object due to loss or gain of e-s. Ex. rubbing a balloon on our hair leaves the balloon -ly charged as it gains e-s from your hair which becomes +ly charged.

  8. The buildup of electric charges on an object • static means “not moving”, so the extra e- aren’t leaving an object

  9. Objects with static electricity will stick to each other as opposite charges attract.

  10. Three Ways to Charge an Object • Friction: Rubbing 2 objects against each other can cause e-s to be wiped from one object onto another.

  11. Conduction: When e-s are passed from one object to another through direct contact. Second object gets the same charge as the first object.

  12. Induction: When a charged object is brought near a neutral object, the e-s in the neutral object are rearranged without touching the charged object. Second object gets opposite charge than the first object.

  13. Which of these shows proper induction?

  14. Electrical Charge • Can be Transferred. • Total charge cannot be created or destroyed. (Law of Conservation of Charge). • A charge can be detected by using a device called an electroscope. • Unit for measuring a charge is a coulomb.

  15. Electric Discharge • The loss of static electricity as charges move off an object. • Can be slow, as in clothes from a dryer. • Or fast, as in lightning or when someone gets shocked from someone or something else.

  16. How Lightning Forms

  17. Mythbusters: Safety in a thunderstorm (15 min)

  18. OQ: How is getting a shock from a doorknob similar to lightning? • Both involve protons moving from one place to another. b. Both involve electrons moving from one place to another. c. Both have really high voltage.

  19. Ben Franklin and the kite • In 1751, Benjamin Franklin experimented with electricity in a thunder storm, using a kite, a key and a Leyden jar (two conductors separated by an insulator; it is a device for storing static electricity). The thunder cloud leaked electrons (negatively-charged particles) down through the kite's silk sting to the key and into the Leyden jar (on the ground). Franklin himself was insulated from the electricity; he was holding the portion of the string attached to the string but not directly to the Leyden jar. When Franklin touched the key, he got a static shock. DO NOT TRY THIS - many people have died trying it. In 1752, Franklin developed the lightning rod.

  20. 05/11 Current Electricity Notes IQ: Going down a plastic slide and getting a static charge is an example of conversion from: • Chemical to mechanical energy • Nuclear to electrical energy • Mechanical to light energy • Mechanical to electrical energy

  21. 5/27 Current Electricity/Circuits IQ: Identify the following objects as motor, generator, solenoid, electromagnet:

  22. Conductors • A conductor allows charges/e-s to flow easily • Some conductors are better than others Examples: Copper Iron

  23. Insulators • An insulator prevents electric charges from flowing easily, Examples: Rubber Cork Wood Plastic

  24. Current Electricity

  25. Electric Current • Electric Current is the flow of electrons/charge through a conductor. SI unit ampere. • There are two types of electric current: Alternating Current Direct Current

  26. Alternating Current (AC) • Changes direction at a regular rate. • Most commonly used type of electricity because it does not create as much heat Examples: Appliances Houses Christmas lights

  27. Direct Current (DC) • Always flows in one direction. • Always flows from negative to positive Example: Battery • Creates a lot of heat

  28. Voltage • Electrical pressure (pushes current) Atoms that are short electrons and atoms with extra electrons • Unit of measure is the volt • Measured with a voltmeter

  29. Current • The directed movement of electrons or the flow. (pushed by voltage) • Unit of measure is the amp or ampere • Measured with an ammeter or amp meter

  30. Resistance • Opposition to current flow (anything that slows down current), mostly a load. • Unit of measure is the ohm • Measured with an ohmmeter

  31. Higher resistance would mean ______ (higher, lower) heat produced in a circuit. Explain.

  32. What is a Battery? • A series of electrochemical cells • Two types: A wet cell A dry cell

  33. What is a circuit? • The path an electric current follows • Consists of four parts: 1.Source:Something to get the power from. Ex. battery, power line. 2. Load: Something that will use the power 3. Wires: To conduct the electricity 4. Switch: To open or close the circuit, not essential. Current flows only through a closed circuit. Brainpop on circuits

  34. Simple Circuit diagram (copy on left page) Scientists usually draw electric circuits using symbols; cell lamp switch wires

  35. Diagram of a Circuit (copy)

  36. Give some examples of loads that may be found in your kitchen.

  37. In which of the following circuits will the bulb NOT light up and why?

  38. What is a series circuit? • A circuit where current follows only one path. Connected back to back. • Diagram:

  39. Series Circuit • If one light goes out, the whole circuit goes out. • If more bulbs are added all of the bulbs get dimmer. • Uses: • Automatic doors • Alarms

  40. OQ: Christmas lights are connected in series. What would happen if you pulled one bulb out? Why?

  41. 5/29 Parallel Circuits IQ: Which of the following is/are NOT required to make a circuit work? • A source • Wires • A magnet • A load • A switch

  42. What is a parallel circuit? • Current follows more than one path. Connected in parallel setup.

  43. Parallel Circuit • If one light goes out, the others remain on. • If more bulbs are added all of them will still glow at full brightness. • Used in: Homes Schools Buildings

  44. Series or parallel?

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