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Capacitors and/or TV ( not Emf)

Capacitors and/or TV ( not Emf). RC CIRCUITS. 1. An empty capacitor does not resist the flow of current, and thus acts like a wire . 2. A capacitor that is full of charge will not allow current to flow, and thus acts like a broken wire . RC Circuits.

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Capacitors and/or TV ( not Emf)

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  1. Capacitors and/or TV (not Emf)

  2. RC CIRCUITS 1. An empty capacitor does not resist the flow of current, and thus acts like a wire. 2. A capacitor that is full of charge will not allow current to flow, and thus acts like a broken wire.

  3. RC Circuits When the switch is closed, the capacitor will begin to charge.

  4. RC Circuits If an isolated charged capacitor is connected across a resistor, it discharges:

  5. 1990B3p.47 A battery with an emf of 24 V and an internal resistance of 1 Ω is connected to an external circuit as shown above.

  6. 1990B3 p.47 a.Calculate the equivalent resistance of the combination of the 4Ω, 8Ω, and 12Ω resistors RS = 4 + 8 = 12 Ω = 6 Ω

  7. 1990B3 p.47 b.Calculate the current in the 5 Ω resistor RE = 5 + 1 + 6 = 12 Ω = 2 A

  8. 1990B3 p.47 c. Calculate the terminal voltage, VAC of the battery VT = E - I r = 24 V - (2 A) (1 Ω) = 22 V

  9. 1990B3 p.47 d. Calculate the rate at which energy is dissipated in the 12 Ω resistor Current splits at B with 1 A through each branch P = I2 R = (1 A)2 (12 Ω) = 12 W

  10. 1990B3 p.47 e. Calculate the magnitude of the potential difference VBC VBC = I R = (2 A) (6) Ω = 12 V

  11. 1998B4p.58 In the circuit shown above, A, B. C, and D are identical light bulbs. Assume that the battery maintains a constant potential difference between its terminals (i.e., the internal resistance of the battery is assumed to be negligible) and the resistance of each light bulb remains constant.

  12. 1998B4 p.58 a. Draw a diagram of the circuit in the box , using the symbols to represent the components in your diagram. Label the resistors A, B. C, and D to refer to the corresponding light bulbs.

  13. 1998B4 p.58 b. List the bulbs in order of brightness, from brightest to least bright. If any two or more bulbs have the same brightness, state which ones. Justify your answer. A > D > B = C A has the largest current VD = VC + VB so D is brighter than C or B C and B are in series = same current

  14. 1998B4 p.58 c. Bulb D is then removed from its socket. i. Describe the change in the brightness, if any, of bulb A when bulb D is removed from its socket. Justify your answer. The brightness of bulb A decreases. REq increases, IA decreases

  15. 1998B4 p.58 ii. Describe the change in the brightness, if any, of bulb B when bulb D is removed from its socket. Justify your answer. The brightness of bulb B increases. The current through bulb B increases, voltage across B increases

  16. 2003B2p.47 A circuit contains two resistors (10 Ω and 20 Ω) and two capacitors (12 μF and 6 μF) connected to a 6 V battery, as shown in the diagram above. The circuit has been connected for a long time.

  17. 2003B2 p.47 a. Calculate the total capacitance of the circuit. = 4x10-6 F

  18. 2003B2 p.47 b. Calculate the current in the 10 Ω resistor. = 0.2 A

  19. 2003B2 p.47 c.Calculate the potential difference between points A and B. VAB = V20 = IR20 = (0.2 A)(20 Ω) = 4 V

  20. 2003B2 p.47 d.Calculate the charge stored on one plate of the 6 μF capacitor. Q = CTV = 4x10-6 F (4 V) = 16x10-6 C

  21. 2003B2 p.47 e.The wire is cut at point P. Will the potential difference between points A and B increase, decrease, or remain the same? Justify your answer. ___increase ___decrease ___remain the same  No current flows through A-B so it does not affect the potential difference

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