Exploring Electromagnetic and Mechanical Waves in Physics Class

1. April 19, 2018 • Complete warm-up sheet – 10 minutes • Electromagnetic vs mechanical, transverse vs longitudinal, light vs sound, medium, frequency, wavelength, amplitude, crest, trough, compression, rarefaction – not just vocab, but properties, relationships, compare/contrast, etc. • Agenda: Review, Waves BrainPop, Test, Finish Bill Nye (if time) • Homework: USA Test Prep due Friday

2. Test • Write on the test • Put your name on the test • Put your score on the test after inputting your answers CAREFULLY into i-Respond • After the test – read Science World

3. Test Standards • S8P4. Obtain, evaluate, and communicate information to support the claim that electromagnetic (light) waves behave differently than mechanical (sound) waves. • a. Ask questions to develop explanations about the similarities and differences between electromagnetic and mechanical waves. (Clarification statement: Include transverse and longitudinal waves and wave parts such as crest, trough, compressions, and rarefactions.) • f. Develop and use a model (e.g., simulations, graphs, illustrations) to predict and describe the relationships between wave properties (e.g., frequency, amplitude, and wavelength) and energy.

4. April 19, 2018 • Warm-Up: Complete both the BrainPop quiz as an anticipation guide and the Ohm’s Law Calculations • Take out 17.3 notes & agenda if you completed them • HOMEWORK: Read/notes chapter 17, sec 4. USA Test Prep due TOMORROW. • Start reviewing for the EOC NOW – don’t wait for me! There are resources on the blog – USA Test Prep – BrainPop – Quizlet – your notes, etc.

5. Which is an example of static electricity? • A. A flashlight shining • B. A radio playing • C. An overhead light burning • D. A balloon sticking to a wall

6. Which is an example of static electricity? • A. A flashlight shining • B. A radio playing • C. An overhead light burning • D. A balloon sticking to a wall

8. Basic Facts •The size of the electric force between two objects depends on thesizeof the charges exerting the force and the distance between the objects. (Think of GRAVITY) •Charged objects exert a force on each other and can cause each other to move. •Objects become charged when they gain or lose electrons.

9. Remember the electron??

10. The law of electric charges states that like charges repel and…

11. …opposites attract

12. How does an object gain or lose electrons? Electrons can move! • They can jump or flow! • They can exert a force! • They can be moved by friction, conduction, or induction

13. How do objects become charged? • Objects may become charged by friction, conduction, or induction.

15. Friction a force that opposes motion between two surfaces that are in contact Charging happens when electrons are “wiped” from one object onto another.

16. Conduction The transfer of thermal energy from one substance to another through direct contact. Charging happens when electrons move from one object to another by direct contact.

17. Induction the generation of fields by interactions between these quantities without direct contact Charging by induction happens when charges in an uncharged metal object are rearranged without direct contact with a charged object.

18. Source: Holt, Rinehart, and Winston

19. Insulators and Conductors • Insulators are poor conductors and resist charge movement while conductors are poor insulators and tend to allow charges to easily move. • Examples of insulators include wood, plastic, and glass • Examples of conductors include metals and salt water

20. Good facts to know: • Charges are not created or destroyed and are said to be conserved. • Charges move easily in conductors but do not move easily in insulators. • Static electricity is the buildup of electric charges on an object. It is lost through electric discharge. Just like HEAT!!!

21. Electroscope Troubleshooting • Make sure your cup is taped well to the pie pan • Make sure your pith (aluminum ball) touches the lip of the pie pan • Make sure the pith drops straight down and can swing freely • After rubbing the balloon on your arm (not head – ick), bring it slowly towards the pith

22. Current Electricity • Electricity that is caused by flowing electrons • An electric circuit allows electrons to flow from a negative pole (more electrons) to a positive pole (fewer electrons).

24. AC/DC – it’s not just your parent’s band DC current – current flows only one way; this is what we get from batteries AC current – current flows both ways; this is what we get from power plants and our wall sockets

25. Solar cells and batteries convert radiant energy or chemical energy into electrical energy.

26. Power plants convert mechanical energy into electrical energy. The turbine could be moved by water or wind! This coal could be replaced by natural gas or nuclear energy! A solar field can heat the water as well!

27. Ohm’s Law • Ratio of voltage to current is consistent, and the ratio is the resistance • Formula: V = IR • V = voltage • I = current • R = resistance • Ohm’s Law is the relationship between the three

28. V = IR • Voltage is a measure of the force that moves charges; potential difference • Voltage is measured in volts, V • Current is the movement of charges • Current is measured in amperes, or amps, A • Resistance is the resistance of a material to current • Resistance is measured in Ohms, Ω

30. Resistance – trying to slow the flow Voltage – the “push” behind the current Current – the charges trying to flow

31. Circuits consist of an energy source, a load, wires, and, in some cases, a switch.

32. A closed circuit is ON!

33. An open circuit is OFF!

34. All parts of a series circuit are connected in a single path. They share the current equally and so get dimmer every time another bulb is added! In a series circuit, the total resistance in the circuit is equal to the sum of each resistance

35. With two bulbs sharing in a series, the light is dim. With three bulbs sharing, it’s even dimmer.

36. What happens if you remove a bulb? In a series circuit, the loads are all on or all off!

37. The loads in a parallel circuit are on separate branches. The electricity can take multiple paths, so the bulbs don’t need to share – they are all equally bright. In a parallel circuit, adding more elements to the circuit causes the total resistance of the circuit to decrease rather than increase.

38. Equal in brightness with 1, 2, or even 3 bulbs.

39. What happens if you remove a bulb? In a parallel circuit, there are multiple paths. Removing a bulb still allows the other bulbs to remain lit.

40. Key Points - Circuits • Circuits consist of an energy source, a load, wires, and, in some cases, a switch. • All parts of a series circuit are connected in a single loop. The loads in a parallel circuit are on separate branches. • Circuits fail through a short circuit or an overload. Fuses or circuit breakers protect against circuit failure. • It is important to follow safety tips when using electrical energy.

41. Something to think about… • Do you think your house is wired on a series or a parallel circuit??

42. If you said, “parallel” you are correct! If your house were wired on a series circuit, all your lights would be either on or off at the same time…how well would that work??