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1984 Circuits 21. Which two arrangements of resistors shown above have the same resistance between the terminals? (A) I and II (B) I and IV (C) II and III (D) II and IV (E) III and IV 22. In the circuit shown above, what is the value of the potential difference between points X and Y if the 6-volt battery has no internal resistance? (A) 1 V (B) 2 V (C) 3 V (D) 4 V (E) 6 V Total resistance 4 + ( 1/3 + 1/6 ) -1 = 6 Current = I = V/R 6 V / 6 = 1 A V = 1 A 4 = 4 V Therefore 2 V will be left for the parallel network More glow more flow 23. A lamp, a voltmeter V , an ammeter A , and a battery with zero internal resistance are connected as shown above. Connecting another lamp in parallel with the first lamp as shown by the dashed lines would (A) increase the ammeter reading (B) decrease the ammeter reading (C) increase the voltmeter reading (D) decrease the voltmeter reading (E) produce no change in either meter reading Questions 24-25 relate to the five incomplete circuits below composed of resistors R, all of equal resistance, and capacitors C , all of equal capacitance. A battery that can be used to complete any of the circuits is available. 24. Into which circuit should the battery be connected to obtain the greatest steady power dissipation? 2 4 ( ½ + ½ ) -1 = 1 (1/4 + 1/4 ) -1 = 2 P=IV (A) R T = 2R I = V / 2 R P =V 2 / 2R (B) No current (C) Same as A (D) R T =(1/R+1/R) -1 =1/2 R Ι= V/1/2R P=2V 2 /R (E) R T =R+(1/R+1/R) -1 =3/2 R I=V/3/2R P=2/3V 2 /R 2 R ½ current 2 R ½ current R= 3/2 R 2/3 current 0 current ½ R 2x current

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25. Which circuit will retain stored energy if the battery is connected to it and then disconnected? B because the capacitor can not discharge 26. A parallel-plate capacitor is charged by connection to a battery. If the battery is disconnected and the separation between the plates is increased, what will happen to the charge on the capacitor and the voltage across it? (A) Both remain fixed. (B) Both increase. (C) Both decrease. (D) The charge increases and the voltage decreases. (E) The charge remains fixed and the voltage increases. Since Capacitance is inversely related to distance between the plates then capacitance decreases. Capacitance is the ratio of the stored charge to the voltage. A decrease in capacitance will result in an increase in voltage C = e o A C = Q d V The charge remains fixed, the capacitor has not been dischared. 27. The five resistors shown below have the lengths and cross-sectional areas indicated and are made of material with the same resistively. Which has the greatest resistance? R = ρ l the length is longer A the area is the least 28. Two capacitors are connected in parallel as shown above. A voltage V is applied to the pair. What is the ratio of charge stored on
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