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Standards/Plan

Standards/Plan. Standards. Standards. Standards. Standards. WARM UP. NO WARM UP TODAY! . 10 minutes to finish your Lifemap!. Simple Harmonic Motion (SHM).

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Standards/Plan

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  1. Standards/Plan

  2. Standards

  3. Standards

  4. Standards

  5. Standards

  6. WARM UP

  7. NO WARM UP TODAY! 10 minutes to finish your Lifemap!

  8. Simple Harmonic Motion (SHM) 1) An electron is fired up between two charged plates, as shown. Which of the following identifies the field and motion of the electron as it passes through the field?

  9. Simple Harmonic Motion (SHM) 2) An insulating plate is rubbed with a cloth to give it a charge. A conducting plate, attached to an insulating handle, is then placed on top of the insulator and briefly grounded by touching it. The conductor is held by the insulating handle and lifted from the insulator plate. Which of the following is true?

  10. Simple Harmonic Motion (SHM)

  11. Warm Up 3) If the voltage across a circuit is kept constant and the resistance is halved, by what factor does the circuit’s current change? a) 1/2 c) 1/4 b) 2 d) 4 4) If the current supplied to a resistor is tripled,, by what factor does the circuit’s power change? a) 1/3 c) 1/9 b) 3 d) 9

  12. Warm Up 5) A computer monitor runs on 120 Volts, and has a resistance of 100 ohms. The amount of power it dissipates is closest to:

  13. Warm Up 5)

  14. Warm Up 6) What is the equivalent resistance of the circuit?

  15. Warm Up 7) A battery (of voltage V or 2V) and resistors (of R or 2R) are connected in various combinations as shown below. In which circuit is the most power dissipated?

  16. Warm Up

  17. Lesson

  18. Electricity and Circuits The movement of electrons is called ELECTRICITY!!!

  19. I - current in amperes Q - charge in Coulombs t - time in seconds. Current V - Voltage in volts I - Current in amps t - Resistance in ohm P - Power in Watts

  20. Series Circuits with multiple resistors • A circuit in which there is only one current path

  21. Series Circuit • Current is the same in all resistors I = I1 = I2 = I3 = I4 • Voltage is distributed among the resistors depending on resistance. V = V1 + V2 + V3 • Total Resistance is the sum of all resistors. RT= R1 + R2 + R3

  22. Parallel Circuits • A circuit in which there are several current paths

  23. ParallelCircuit- Rules CHANGE!! • Current is the added in all resistors IT = I1 + I2 + I3 • Voltage is equal among the resistors VT = V1 = V2 = V3 • Total Resistanceis the reciprocal of all resistors 1/RT = 1/R1 + 1/R2 + 1/R3

  24. Kirchhoff’s Rule - NEW • Junction Rule – total CurrentINto a junction must equal the total CurrentOUT of the junction:

  25. Sample problem • Find the current I4 (magnitude and direction). 3.0 A I4 1.5 A 4.0 A

  26. You Try! • 1) Current in WX: 3) Current in ZB • 2) Current in XZ

  27. Combination Circuits • Some circuits have both SERIES and PARALLEL parts to them. These are called COMBINATION circuits. They are difficult

  28. Step 1: Simplify the circuit to find Total R • Step 2:Get the TOTALCURRENT • Step 3: IT = Iseries • Step 4: Solve each piece separately

  29. Announcements Turn in progress reports Circuits_ Assignment 2 Circuits QUIZ on Friday!

  30. Circuits FR_2: Student led response IF given 120V, the bulbs would be 60W. But based on the set up of the circuit they are not going to get 120V

  31. Miscellaneous Info WHITEBOARDS You know that drawer in the kitchen where you put all the random stuff that doesn’t exactly go anywhere else?

  32. Miscellaneous Info • Internal Resistance • Resistivity • Ohmic Resistors

  33. 9V batteries actually produce MORE THAN 9V • This is because in the real world batteries have a small amount of INTERNAL RESISTANCE.

  34. Electro Motive Force vs. Voltage Emf = V for a battery with no “internal resistance”

  35. EMF =  The voltage the battery actually produces ΔV = Terminal Voltage The voltage the battery provides to the circuit

  36. Example • The internal resistance of a 1.5 V cell is 4 . What is its terminal voltage (actual voltage) when it is supplying 2 mA of current?

  37. Example • A battery has an emf of 12.0 V and delivers 150.0 mA when connected to a 75.0  load. What is the internal resistance of the battery?

  38. 1) In the circuit, the emf, ,produced by the battery is 24V, and the load resistance of R is 10 Ω. If the ammeter reads 2.0A in the circuit, what is the terminal voltage of the battery? 2) What is the internal resistance of the battery?

  39. Miscellaneous Info • Internal Resistance • Resistivity • Ohmic Resistors

  40. So what actually determines the resistanceof an a resistor?

  41. So what actually determines the resistanceof an a resistor? L: length of resistor (m) A: cross sectional area of resistor (m2) : resistivity ( m) • LENGTH • CROSS SECTIONAL AREA • MATERIAL

  42. Resistivity, ρ –is a property of the material. • low ρ  conductors high ρ  insulators

  43. Sample problem • What is the resistivity of a substance which has a resistance of 1000 W if the length of the material is 4.0 cm and its cross sectional area is 0.20 m2?

  44. Sample problem 2 • What is the resistance of a mile (1600m) of copper wire if the diameter is 5.0 mm?

  45. Conceptual 1 • A certain wire has resistance R. The resistance of another wire, identical with the first except for having twice its diameter, is

  46. Conceptual 2 • Wire 1 has a length L and a circular cross section of diameter D. Wire 2 is constructed from the same material as wire 1 and has the same shape, but its length is 2L, and its diameter is 2D. Is the resistance of wire 2: • (a) the same as that of wire 1 • (b) twice that of wire 1 • (c) half that of wire 1

  47. Conceptual 3 • The five resistors shown below have the lengths and cross‑sectional areas indicated and are made of material with the same resistivity. Which resistor has the least resistance?

  48. Individual Practice • A metal wire 10 m long has a cross-sectional area of 1  10-3 m2. The resistivity of the metal is 1.2  10-8  m. • What is the resistance of the wire? • What is the resistivity if the diameter of the wire is doubled? • What is the resistance if the diameter of the wire is doubled? • What is the resistance if the length of the wire is doubled?

  49. Miscellaneous Info • Internal Resistance • Resistivity • Ohmic Resistors

  50. Ohmic Resistors • Graphs w/ Circuits • The super simple version

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