1. The document discusses capacitors and capacitance, including parallel plate capacitors. It defines capacitance as the ability to store separated charge.
2. For a parallel plate capacitor, the capacitance is given by C = ε0A/d, where ε0 is the permittivity of free space, A is the plate area, and d is the plate separation.
3. Capacitors can be connected in parallel or in series. For capacitors in parallel, the total capacitance is the sum of the individual capacitances. For capacitors in series, the total capacitance is given by 1/(1/C1 + 1/C2).
17. A parallel plate capacitor given a charge q. The plates are then pulled a small distance further apart. What happens to the charge q on each plate of the capacitor? ACT: Parallel Plates 1) Increases 2) Constant 3) Decreases Remember charge is real/physical. There is no place for the charges to go. +q -q + + + + - - - - d pull pull
18. A parallel plate capacitor given a charge q. The plates are then pulled a small distance further apart. Which of the following apply to the situation after the plates have been moved? 1)The capacitance increases True False 2)The electric field increases True False 3)The voltage between the plates increases True False Preflight 4.1 +q -q + + + + - - - - d pull pull
19. A parallel plate capacitor given a charge q. The plates are then pulled a small distance further apart. Which of the following apply to the situation after the plates have been moved? ACT/Preflight 4.1 The energy stored in the capacitor A) increases B) constant C) decreases +q -q + + + + - - - - d pull pull
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21. Two identical parallel plate capacitors are shown in end-view in A) of the figure. Each has a capacitance of C. A ) B ) If the two are joined as in (B) of the figure, forming a single capacitor, what is the final capacitance? 1) 2C 2) C 3) C/2 ACT/Preflight 4.2
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33. A circuit consists of three initially uncharged capacitors C 1 , C 2 , and C 3 , which are then connected to a battery of emf . The capacitors obtain charges q 1 , q 2 ,q 3 , and have voltages across their plates V 1 , V 2 , and V 3 . 1) q 1 = q 2 Not necessarily C 1 and C 2 are NOT in series. 2) q 2 = q 3 Yes! C 2 and C 3 are in series. ACT/Preflight 4.4: Which is true? C 2 C 3 C 1 E + - -q 2 +q 1 -q 1 +q 3 -q 3 +q 2 V 1 V 2 V 3
34. 1) V 2 = V 3 Not necessarily, only if C 1 = C 2 2) E = V 1 Yes! Both ends are connected by wires A circuit consists of three initially uncharged capacitors C 1 , C 2 , and C 3 , which are then connected to a battery of emf . The capacitors obtain charges q 1 , q 2 ,q 3 , and have voltages across their plates V 1 , V 2 , and V 3 . ACT/Preflight 4.4: Which is true? C 2 C 3 C 1 E + - -q 2 +q 1 -q 1 +q 3 -q 3 +q 2 V 1 V 2 V 3 10V 0V 7V??
35. 1) V 1 < V 2 Nope, V 1 > V 2 . (E.g. V 1 = 10-0, V 2 =10-7) 2) C eq > C 1 Yes! C 1 is in parallel with C 23 A circuit consists of three initially uncharged capacitors C 1 , C 2 , and C 3 , which are then connected to a battery of emf . The capacitors obtain charges q 1 , q 2 ,q 3 , and have voltages across their plates V 1 , V 2 , and V 3 . ACT/Preflight 4.4: Which is true? C 2 C 3 C 1 E + - -q 2 +q 1 -q 1 +q 3 -q 3 +q 2 V 1 V 2 V 3 10V 0V 7V??
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Notes de l'éditeur
Electric potential energy Potential difference PED = qV V = Ed
Use fire extinguisher analogy?
Stores energy….electrical potential energy. If the plates were free to move, they would collapse on each other. Just like releasing a brick from height h above the floor. Or, if charges were free to move, the capacitor would “discharge”. Demo. Can I make U more plausible?
Here note that this is small number for such a big device. How do they make “real” capacitors?
