PLC Activity #7 Resistive Circuits Due: see website for due dates How to get credit for this activity First, sign-in at the computer and sign-out when the activity is complete. Show your work and results to a PLC tutor so they can check your work and initial the signoff sheet. Be prepared to answer questions about the activity or your results. Part 1: DC Circuit Physlets Go to Chapter 30: DC Circuits. Do the following Physlet Physics exercises and answer the questions listed. Problem 30.3 Answer the following questions for each circuit in this animation. Assume an ideal battery (no internal resistance) and ideal meters but note that the battery and unknown resistor are different for each circuit (electric potential is given in volts and current is given in mA). Use the slider to change the variable resistor. a. What is the resistance of the unknown resistance and the voltage of the battery in each circuit? b. What is the range of power dissipated for each circuit over the full range of variable resistance values? Problem 30.4 Rank the three resistors (from smallest to largest) in each of the two circuits (ammeter current is given in amperes). a. Circuit 1 b. Circuit 2 Physlet Problem 30.6 What is wrong with these circuits? Close the switches to see what happens and then explain what is wrong. Note which circuit elements are destroyed (electric potential is given in volts and resistance is given in ohms). Choose a new circuit after a circuit element is "destroyed." a. Circuit 1 b. Circuit 2 c. Circuit 3 (Hint: What might the power rating be on the resistor?) 1 Part 2: Conceptual and Ranking Problems Question 1 In the circuit the narrow resistor is made of the same material as the thick connecting wires. Assume steady state. a. Which graph (1a – 1f) correctly shows the magnitude of the E-field at locations around the circuit? Explain your answers. b. Which graph (2a – 2f) correctly shows the drift speed of the electrons at locations around the circuit? Explain your answers. Question 2 In the circuit the narrow resistor is made of the same material and is half as thick as the thick connecting wires. Assume steady state. Before attempting to answer these questions, draw a copy of this diagram. a. (i) On your diagram, show the E-field at the locations indicated, paying attention to relative magnitude. (ii) Is the field larger at point D or G? By how much larger is it? (iii) Is the drift velocity larger at point D or G? By how much larger is it? b. (i) Carefully draw pluses and minuses on your diagram to show the approximate surface charge distribution that produces the E-field you drew. Make your drawing show clearly the difference between regions of high (and low) surface charge density. (ii) Which region has the highest and lowest surface charge density? c. Use your diagram to determine which of the following statements about this circuit are true. Explain your answers. 1. There is a large gradient of surface charge on the wire between locations C and E. 2. The electron current is the same at every location in this circuit. 3. Fewer electrons per second pass location E than location C. 4. The magnitude of the E-field is the same every location in this circuit. 5. The magnitude of the E-field at location D is larger than the magnitude of the Efield at location G. 6. There is no surface charge at all on the wire near location G. Part 3: Mystery Circuits 2 There are three mystery circuits that consist of an unknown combination of series and parallel connections. You should try the following experiments to aid in your investigation: remove one lamp from its socket and see how it affects the brightness of the remaining lamps or short out one lamp and see how it affects the brightness of the remaining lamps. For each mystery circuit, discuss the results of the above experiments with your group members and then draw your best guess for how the lamps are connected. Mystery Circuit 1: Mystery Circuit 2: Mystery Circuit 3: Mystery Circuit 4: 3