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Electricity and Magnetism  Electricity

Electricity and Magnetism  Electricity. Section 1 – Electric Charge and Static Electricity. Balloon and can activity Balloon confetti. Recall: What are the parts of the atom and their charges?. 1.Proton 2.Neutron 3.Electron. Positive charge Neutral – No charge Negative charge.

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Electricity and Magnetism  Electricity

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  1. Electricity and MagnetismElectricity

  2. Section 1 – Electric Charge and Static Electricity • Balloon and can activity • Balloon confetti

  3. Recall: What are the parts of the atom and their charges? • 1.Proton • 2.Neutron • 3.Electron Positive charge Neutral – No charge Negative charge

  4. How are protons, neutrons, and electrons arranged in an atom?

  5. What happens when: They repel! They Repel They attract!

  6. So... • Charges that are the same repel each other and charges that are different attract each other.

  7. In what other situation do opposites attract?

  8. Magnetism = magnetic poles interact. (north and south) Opposites attract and like poles repel • Electricity = opposite charges attract and like charge repel

  9. Magnetism vs. Electricity • Magnetism • Poles can’t exist on their own…. Always N and S together • Electricity • Positive charges can exist without negatives

  10. ELECTRIC FORCE • = the attraction or repulsion between electric charges • Electric charges can exert their force over a distance. The region where that force is is called an “electric field”. • ….what does this remind you of?

  11. Electric Fields • You can represent them using electric field lines Try to draw the field for 2 positive charges next to each other and for a positive and a negative charge.

  12. Review: • Electrons carry a negative charge while protons carry positive charge. • The objects around us contain billions and billions of atoms, and each atom contains many protons and electrons. • The protons are located in the center of the atom, concentrated in a small area called the nucleus. • The electrons are in motion outside of the nucleus in orbitals. • The protons are basically trapped inside the nucleus and can't escape the nucleus. As a result, it is moving electrons that are primarily responsible for electricity.

  13. Static Discharge • Most atoms have an even number of protons (+ charges) and electrons (- charges). What is the overall charge of this and most atoms?? NEUTRAL

  14. In some materials (especially metals), electrons are held pretty loosely. They can move to other atoms.

  15. What would happen if an atom LOST an electron?

  16. What would happen if an atom GAINED an electron?

  17. Can you see Electric charge? • What kind of instrument detects charge? • (page 40)

  18. Static Discharge • Charges that build up in static electricity don’t stay like that forever. • Atoms and objects prefer to be neutral • When a negatively charged object and a positively charged object are brought together, electrons transfer until both objects have the same charge. • Static Discharge = loss of static electricity as electric charges transfer from one object to another

  19. Electricity • The most commonly- observed form of electricity is probably lightning. Lightning is a big spark that occurs when lots of electrons move from one place to another very quickly. • There are three basic forms of lightning, cloud to cloud, cloud to surface, and surface to cloud. All are created when there is an unequal distribution of electrons.

  20. Section 2 Electric Current

  21. Lightning is a quick release of a huge amount of electrical energy. • Unfortunately, it cannot be used to power a TV or appliances because it only lasts for a second. • Instead…..devices need continuously flowing electric charges

  22. Is static electricity continuous? Do the electric charges flow continuously? NO…. The charges build up for a while and do not go anywhere. Then, in static discharge, they travel really fast and it lasts only for an instant.

  23. What is it called when electric charges flow continuously through a material such as a wire? • An ELECTRIC CURRENT!

  24. The RATE of the electric current • Is the amount of charge that passes through the wire in a unit of time • The UNIT for rate of a current is called…. The AMPERE ……also known as the AMP. It is the charges flowing past a given point each second. FUN FACT: It’s named after Marie Ampere… a scientist who studied electricity. See page 44-45

  25. An electric current (continuously flowing electric charges) need a specific PATH to follow. The name for this PATH that the charges travel on is an ELECTRIC CIRCUIT. Compare to : cars on a race track. If part of the track is missing…. What are the cars going to do? What types of electrical devices have electric circuits?

  26. DO NOW • Brainstorm types of materials that are often used in cooking. • Think of types of materials that are used for protection in cooking so that you do not burn yourself. • Based on the definition of electricity, why do you think some materials are good at conducting electricity and others are not?

  27. Wires are usual made of metal. Would a circuit with wires made from plastic or string have the same effect? • No….. Different materials have different properties.

  28. A Conductor transfers electric charge well. • An insulator does not transfer electric charge well

  29. CONDUCTORS • Ex: metals – silver/copper/aluminum/iron • Charges flow easily through these materials. • The electrons of the atoms are held loosely so they move throughout the material easily! • Electrons flow and carry an electric current and electric charge.

  30. Turn on the lights! • Did you ever wonder why a light goes on the instant you flip the switch? How do the electrons get to your lamp from the electric company so fast? The answer is that the electrons are not sent to your house……they are already present inside the conductors of the circuit. When you flip the switch, electrons at one end of the wire are pulled while those at the other end are pushed.

  31. INSULATORS • Ex: rubber/glass/sand/plastic/wood • Charges (electrons ) cannot flow easily because they are bound tightly to their atoms.

  32. So, why don’t you get a shock when you touch an extension cord that is carrying a current?

  33. Contrary to popular belief: • Metals are NOT the only conductors! • Ex: fluorescent light bulbs have a gas that conducts electricity • Ex: some liquids and pastes in batteries conduct electricity

  34. Classwork/ Homework • What is potential energy? • What’s an example of a place with high potential energy? • What’s an example of a place with low potential energy? • What allows a roller coaster to speed down a hill? • How is an electric circuit similar to a roller coaster? What provides the potential energy, and what is potential energy related to? • What is the voltage of a circuit and what is another name for it? • What does voltage cause? • What is another way of thinking about voltage? • What is a voltage source? Why is it necessary? What are examples of voltage sources? How does a voltage source get charges to move?

  35. Potential Energy • Energy an object has as a result of its position, or height. • High potential energy top of hill • Low potential energy  bottom of hill

  36. Why does a roller coaster speed down a hill? • The difference in potential energy! …It moves from high to low

  37. An electric circuit is similar to a roller coaster: • Circuit:: roller coaster’s steel track • Energy source(battery):: roller coaster’s motor

  38. Electric circuit is different than a roller coaster: • Electric circuit’s potential energy is a result of charges in the battery. • BUT • A roller coaster’s potential energy is a result of height differences

  39. The voltage of a circuit : • Is the difference in electrical potential energy between two places in a circuit. • AKA “potential difference”

  40. What does voltage cause? • It causes a current in an electric circuit

  41. Another way of thinking about voltage It’s the amount of FORCE pushing an electric current

  42. A voltage source • It’s a device that creates a potential difference in an electric circuit • It has 2 terminals, so that charges will move • Ex: generator, battery

  43. RESISTANCE • Not only does height difference or “voltage” affect the speed of a roller coaster, but the quality of wheels does too. If they are rusty, the roller coaster cannot travel as easily

  44. Resistance, cont’d • Just like it is hard for rusty wheels to move, some materials make it hard for charges to move through them in a current. You can measure this as RESISTANCE. • The Greater the resistance, the Less current there is for a given voltage

  45. Resistance • Gregory Ohm studied resistance. • The unit to measure resistance is the ohm!

  46. CLASSWORK • 1. What are the 4 factors that determine resistance of a wire (or any object)? • Explain how each affects the resistance of a current • 2. What is the “path of least resistance” and how does it relate to currents? • 3. Why is it safe for a bird to sit on an uninsulated electric fence?

  47. 4 factors that determine resistance • 1. material of wire • Some hold electrons tightly (insulators)(high resistance) and others do not (low resistance) • 2. Length • The longer the wire, the more the resistance • 3. Diameter • The thinner the wire, the more the resistance • 4. temperature of wire • The lower the temperature, the lower the resistance

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