4 th 6 weeks physics BRs

1. 4th 6 weeks physics BRs

2. Bell ringer 1/23 • In a steam turbine that is used to drive an electrical generator, hot steam flows from one end of a tube to another, cooler end. As the steam flows, it turns the turbine, increasing the kinetic energy. Because of the laws of thermodynamics, which must be true about this system? • Only some of the heat energy is converted to kinetic energy. • Output kinetic energy is greater than input heat energy. • Some energy is destroyed during transformation. • The total energy of the system increases over time.

3. Bell ringer 1/24 • Draw and label a bohr model of an atom. Label charges as well.

4. BELL – RINGER 1/31 • Suppose two balloons hanging from strings repel one another. What are the possible charges for the balloons? Draw a free-body force diagram for the balloons.

5. Bell – Ringer 2/5 • What are electric field lines? • Where have you seen these before? • How do electric field lines look around a positive charge? • How do electric field lines look around a negative charge?

6. Bell-Ringer 2/6 • How do we determine if the force between two charges will be attractive or repulsive?

7. 2/19/13 • What type of force is present between a tiger and a rock each with a different mass? • Electrostatic • Gravitational • Repulsive • All of the above

8. 3-1-13 Bell-Ringer: • What is an Electromagnet? • Have you ever heard this word used before? If so, how and where?

9. Bell-Ringer 3-6-13Yes you have to DRAW it! • What is the voltage? • What is the current? • If the voltage were increased to 40V, what would the current be?

10. Bell-Ringer 3-7-13 Use your devices (AKA phones n’ stuff)! You may use a partner if you have no internet. • What does a transformer do? • How do the magnetic stripes on credit cards work? • If gold is a better conductor than copper, why don’t we use gold to wire our homes? • Why is electricity dangerous? • High voltage • High resistance • High current • All of the above

11. Answers • A transformer transfers current from on circuit to another and lowers voltage delivered to the home. • Little bits of iron (magnet) in the strip are correlated to numbers allowing the card reader to interpret the data electronically. • Thievery! It also happens with copper now since its value has increased. • C. Because potential difference creates current!

12. Bell-ringer 3-19 • A long wavelength indicates a ______ frequency, and a short wavelength indicates a _______ frequency. • Can we see all electromagnetic waves? Which electromagnetic waves can we see?

13. Bell-Ringer 3-20 • Write the following questions and leave space between each: • What materials did you use to make your wave machine? • How long is your wave machine? • How long does it take for your wave to return back to the original point of disturbance? (Do three trials)

14. Bell-Ringer 3/21

15. Bell-ringer 3-25 • What are some wave interactions we have discussed in class? (at least two)

16. Bell-Ringer 4/1 • Suppose a whistle has a frequency of 325Hz and the whistle maker knows the length of the whistle should be ¼ the wavelength. The speed of sound is 343m/s. How long should the whistle be?

17. Bell-Ringer 4/9 • Using addition, how many ways can you have a sum of eight using two whole, positive integers? List all.

18. Bell-ringer 4/10 • Name 4 elements that are likely to bond with Fluorine. • Which list of elements share similar chemical properties.? • Li, Be, Ca, O • O, Cl, P, N • H, Na, K, Fr • B,C,N,O

19. Bell-ringer 4/11

20. Bell-Ringer 4/12

21. Bell-Ringer 4/15 • Write the chemical formula for • Beryllium Nitride • Potassium Selenide • Barium Chloride • Lithium Iodide