1 of 5 2/4/2010 3:35 PM Current Score: 0/20 Due: Mon Feb 15 2010 10:15 PM EST Question Points 1 2 3 4 5 0/40/100/40/10/1 Total 0/20 Description This assignment is worth 20 points. Each part is worth 1 point. Assume the numbers given in each problem are accurate to three significant figures. WebAssign expects your answers to be accurate within 1%. If you don't round off until the end, and then round off to three significant figures, you should be fine. Occasionally there are errors in WebAssign. If you are convinced your answer is correct and WebAssign is grading you incorrectly please check with Professor Duffy. 1. 0/4 pointsduffy_ep_ch18_p102 [1324015] Four resistors and an ideal (zero resistance) battery are laid out in a star-shaped pattern, and connected in three different ways, as shown above. The resistors have resistances of R, 2R, 3R, and 4R, as labeled on the diagram. We will give a value for R later, but you don't need to know it to answer the first two parts of this problem. (a) Rank the circuits based on the magnitude of the current through the battery, from largest to smallest. Use only > and/or = signs in your answer, such as C>A=B A=C>B -or- C=A>B (b) In terms of R, what is the equivalent resistance of Circuit A? Just enter the numerical coefficient in front of the R in the answer box 0.48 R
2 of 5 2/4/2010 3:35 PM or the rest of this problem, use these numbers. The battery voltage is 21.0 V, and the value of R is 2.00 ohms. (c) In Circuit A, calculate the magnitude of the current in the battery. 21.9 A d) In Circuit B, calculate the total power dissipated in the resistors. 276 W 2. 0/10 pointsduffy_ep_ch18_p101 [1320330] Circuit a has a battery connected in a circuit with four identical light bulbs (numbered 1 through 4) and three switches (lettered A through C). The switches are shown in their open positions. The battery is ideal - it has no resistance of its own. We will also assume that the resistance of each bulb is the same no matter how much current passes through it. Circuit b is exactly the same as circuit a, except that a fifth light bulb, identical to the other four, has been added to the circuit. (a) In Circuit a, if you want to maximize the brightness of bulb 4, what should you do with the switches? Select all the correct answers Switch A should be open. Switch A should be closed. Switch A doesn't matter - having it open or closed has no effect on bulb 4. Switch B should be open. Switch B should be closed. Switch B doesn't matter - having it open or closed has no effect on bulb 4. Switch C should be open. Switch C should be closed. Switch C doesn't matter - having it open or closed has no effect on bulb 4. (b) In Circuit b, if you want to maximize the brightness of bulb 4, what should you do with the switches? Select all the correct answers Switch A should be open. Switch A should be closed. Switch A doesn't matter - having it open or closed has no effect on bulb 4. Switch B should be open. Switch B should be closed. Switch B doesn't matter - having it open or closed has no effect on bulb 4. Switch C should be open. Switch C should be closed. Switch C doesn't matter - having it open or closed has no effect on bulb 4. (c) In Circuit b, you close all the switches. Rank the bulbs in circuit b by their brightness, from brightest to dimmest, with all the switches closed. Use only > and/or = signs in your ranking, such as 3>2=5>1>4 2>5>3=4>1 -or- 2>5>4=3>1 (d) Starting with all the switches closed in Circuit b, you then open switch B. When you open switch B, what happens to bulbs 3, 4, and 5? Select all the correct answers Bulb 3 gets brighter. Bulb 3 gets dimmer.
3 of 5 2/4/2010 3:35 PM Bulb 3 stays the same. Bulb 4 gets brighter. Bulb 4 gets dimmer. Bulb 4 stays the same. Bulb 5 gets brighter. Bulb 5 gets dimmer. Bulb 5 stays the same. (e) Now, all the switches are closed in both circuits. Which of the following statements are true when all switches are closed? Bulb 2 in Circuit a is brighter than Bulb 2 in Circuit b. Bulb 3 in Circuit a is brighter than Bulb 3 in Circuit b. Bulb 2 in Circuit b is the same brightness as Bulb 5 in Circuit a. Circuit a has more power dissipated in it than does Circuit b. The current through the battery in Circuit a is larger than the current through the battery in Circuit b. The current through Bulb 2 in Circuit a is larger than the current through Bulb 2 in Circuit b. The potential difference across Bulb 4 in Circuit a is larger than the potential difference across Bulb 4 in Circuit b. For the rest of this problem, use these numbers. The battery voltage is 12.0 V, and the resistance of each light bulb is 2.00 ohms. For convenience, the circuit diagrams are shown again here, too, with the switches set as in the questions (f) In Circuit b, with switch A open and switches B and C both closed, calculate the equivalent resistance of the circuit. 1.71 ohms g) In Circuit b, with switch A open and switches B and C both closed, calculate the magnitude of the current in bulb 4. 2 A h) In Circuit b, with switch A open and switches B and C both closed, calculate the magnitude of the potential difference across bulb. 8 V i) Now, we consider Circuit a. In Circuit a, with switch A open and switches B and C both closed, calculate the equivalent resistance f the circuit. 0.8 ohms j) In Circuit a, with switch A open and switches B and C both closed, calculate the power dissipated in Bulb 1. 18 W 3. 0/4 pointswiley Simulation 32.1. [245484]
4 of 5 2/4/2010 3:35 PM eries and Parallel Circuits (a) In this simulation you can choose between seven possible circuits by clicking on one of the small circuit diagrams shown at the upper right. Given the different circuits available to you, and taking into account the limits set by the sliders in the simulation, determine the following. Express your answers to three significant figures. (i) What is the maximum possible total current that can be obtained in this simulation? 30 A (ii) What is the minimum possible total current that can be obtained in this simulation? 0.0333 A (b) Now move the sliders so the resistances of the three resistors are equal to one another. With the battery voltage fixed, rank the circuits according to the following criteria. Use principles of physics to find the answers, and then verify the answers using the simulation. (i) Rank the circuits based on the total current, from largest to smallest. Use only > and/or = signs in your ranking (e.g., 4>3>6>1=7>5>2). 5>4>7>1>6>2>3 (ii) Now rank circuits 2 to 7 only based on the current through resistor R2, from largest to smallest. Use only > and/or = signs in your ranking (e.g., 4>3>6=7>5>2). 4=5>2=7>3=6 -or- 4=5>2=7>6=3 -or- 4=5>7=2>3=6 -or- 4=5>7=2>6=3 -or- 5=4>2=7>3=6 -or- 5=4>2=7>6=3 -or- 5=4>7=2>3=6 4. 0/1 pointsduffy_ep_ch18_p37_var [1332432]
5 of 5 2/4/2010 3:35 PM If the potential difference across the 18 resistor in the figure above is 9.00 V, what is the emf of the battery? Note that you should be able to do this problem without a calculator. 72 V 5. 0/1 pointsduffy_ep_ch18_p38_var [1332433] Four resistors, of resistance R, 2R, 3R, and 6R, are connected together in a circuit with an ideal battery, as shown above. If the magnitude of the current through the 2R resistor in the figure above is 6.00 A, what is the magnitude of the current through the battery? Note that you should be able to do this problem without a calculator. 45 A Assignment Details