Review 2C PHYS 22100 Name Use the sketch shown below to answer the next 3 questions. The sketch shows a region of space with regions of uniform electric potential indicated by dashed lines. Eight different locations are indicated by points I through VIII. -20 V -30 V -40 V 1-50 V 1. At which point (I through V) would an electron have the greatest amount of electric potential energy (PEelec)? A. point I B. point II C. point III D. point IV E. point V 2. Suppose an electron was placed at point V and constrained so that it could only move in the plane of the paper, in which direction would it move? A. To the right B. To the left C. Upwards in the plane of the paper D. Downwards in the plane of the paper E. The force is zero so it won't move. 3. How much potential energy is gained (negative if lost) if we move a +1.00 Coulomb point charge from point VII to point I? A. zero Joules B. +20 Joules C. -10 JoulesD. +10 Joules E. None of the above Use the following description to answer the next 3 questions. An air-filled parallel plate capacitor with plate separation d is connected to a battery that has a potential difference of AV Batt . Without breaking any of the connections, insulating handles are used to decrease the plate separation to - AV Batt 4. When the capacitor's plate separation is decreased, how does the potential difference between the plates change? A. the potential difference does not change B. the potential difference doubles C. the potential difference quadruples D. the potential difference is half as large as it was E. the potential difference a quarter as large as it was. 5. When the capacitor's plate separation is decreased, how does the charge on the positive plate change? A. the charge does not change B. the charge doubles C. the charge quadruples D. the charge is half as large as it was. E. the charge is a quarter as large as it was. 6. After the plate separation was decreased, a dielectric material ( k = 2) is inserted between the plates. How does the charge on the positive plate change compare to when the plates were still separated by distance d (air fills the gap between the plates). A. the charge does not change B. the charge doubles C. the charge quadruples D. the charge is half as large as it was. E. the charge is a quarter as large as it was.7. For the following statements, decide whether it best describes Resistance R, Voltage V, Current I, or Power P. a. measured in parallel to a circuit. b. measured on series to a circuit. C. the amount of energy stored per charge. d. opposition to the flow of electrons. e . the "pressure" pushing the electrons through the circuit. f . measured in amps. g. the same as potential difference. h. the number of Coulombs that pass through a wire each second. i . dependent upon a wire's length. j. measured in amps. K . the number of Coulombs that pass through a wire each second. 1 . dependent on the voltage applied. 8. If you accidentally grabbed the prongs of a partially plugged-in 120-V electrical plug on a day when your skin resistance was 320,000 2. How much current would pass through your body? 9. Circuit A has three light bulbs, each with 6 2 resistance, wired in series. Circuit B has the same size three light bulbs wired in parallel. What is the same for every resistor in series? What is the same for every resistor in parallel? What happens if one light bulb burns out for the series circuit? What happens if one light bulb burns out for the parallel circuit? What is the equivalent resistance for the series circuit? What is the equivalent resistance for the parallel circuit?10. A capacitor is designed to hold at least 100 uJ at an operating voltage of 50 V. (Use this to determine the capacitance needed.) The capacitor is to have an effective length and width of 750 cm by 8.0 cm, respectively. (It will be rolled into a coil, but that is irrelevant to this problem.) The plate separation will be 0.0030 mm. Would using air as the dielectric work? Would using mylar work? Show the calculations for both set ups. Table 26.1 Approximate Dielectric Constants and Dielectric Strengths of Various at Room Temperature Dielectric Strength Dielectric Constant k (106 V/m) Material Air (dry) 1.000 59 4.9 24 Bakelite Fused quart. 3.78 Mylar 3.2 Neoprene rubber 6.7 12 Nylon 3.4 14 Paper 3.7 16 35 11 Paraffin-impregnated paper Polystyrene 2.56 24 Polyvinyl chloride 3.4 40 Porcelain 6 12 Pyrex glass 5.6 14 Silicone oil 15 Strontium titanate 233 8 Teflon 2.1 60 Vacuum 1.000 00 Water 80 a The dielectric strength equals the maximum electric field that can exist in a dielectric electrical breakdown. Note that these values depend strongly on the presence of impu flaws in the materials. 11. A capacitor is made with a capacitance of 3500 pF. Which of the following will increase the capacitance the most? a. doubling the area of the conducting plates. b . cutting the distance between the plates in half. C. doubling the distance between the plates. d. changing the dielectric from air (1.0) to mylar (3.2). 612 . A blow dryer needs to produce 25 kJ of heat every minute. It is to run on a 120-V outlet. Assume the heating element is made of nichrome (resistivity 1.5 x 106 2m), and has a length of 250 cm. a. b . What is the power being used? What is the current through the heating element? What is the resistance of the heating element? What is the radius of the heating element? Assuming the toaster is used 10 minutes a day, 5 days a week, 48 weeks a year. If electricity costs 11.600 per kilowatt-hour, how much does it cost to operate the blow dryer for a year? 13. For a simple circuit, double which of the following factors would made the biggest difference in the power consumed? Which would make the least significant change? Voltage, Resistance, or Current? 14. What is the difference between calculating the equivalent resistance or capacitance for series and parallel circuits? 15. Show from the primary units how the time constant units end up being seconds.16. For the circuit shown, find the following: The equivalent resistance. If it is helpful, redraw the circuit to make parallel and series more a. obvious. b. The current delivered by the battery. C . The power delivered by the battery. Find the voltage drop over each resistor. R1=40 0 R2=30 02 AAAAA AAAAA 120. V AAAAA R3=80 0 R4=40 0 AAAAA AAAAA AAAAA Rs=20 0 R6= 10 0 17. Consider the following circuit: find V and I for each resistor. R1=20092 R2=2008 A 12.00V R3=80012 C18. Connect the following resistors in series and connect the meter to measure the voltage drop over resistor B. B Br Yel BBTM 12 V dc BK Vio R R gold silve CE V2 mA MULTIMETERCOM Find the following: COM b. Resistance A = c. Resistance B = d. Total Resistance = e. Anticipated Current = f. Voltage drop over A = g. Voltage drop over B = h. Current through A = i. Current through B =19. Connect the following resistors in parallel and connect the meter to measure the total current. A Br Yel 12 V dc BK Vio R 0 0.0 3BTM gold silve gold DCV DCA BBY b. Resistor A = MAN CE c. Resistor B = VS mA DT830D DIGITAL MULTIMETER OVCON- d. Resistor C = BBTM COM e. Total Resistance = f. Anticipated Total Current = g. Voltage Drop over A = h. Current through A = i. Current through B = j. Current through C = 20. (a) What is the terminal voltage of a large 1.54-V carbon-zinc dry cell used in a physics lab to supply 1.50 A to a circuit, if the cell's internal resistance is 0.200 ? (b) How much electrical power does the cell produce? (c) What power goes to its load? 10