Chemistry Hour Exam 1

Transcription

1 Chemistry Hour Exam 1 Fall 23 Department of Chemistry Michigan State University East Lansing, MI Name Student Number Question Points Score Total 15 Answer any 7 of the 9 questions. All parts of a given problem are worth the same number of points unless noted in the problem. The number of points earned on this exam will be added to your total points for determination of the final course grade. Notice that you may earn 5 bonus points above the advertised 1 points for this exam. Do your work on these pages. Use the backs of the pages for extra space if necessary. The exam is closed book. Calculators are not allowed. Thursday, October 16,

2 Question 1. An experiment produces three periodic signals, A, B, C. Two cycles of these signals are shown below Signal A (volts) Time (milliseconds) Figure 1 - Signal A 1.2 Signal B (volts) Time (milliseconds) Figure 2 - Signal B 1.2 Signal C (volts) Time (milliseconds) Figure 3 - Signal C Thursday, October 16,

3 The first ring (time = 1 milliseconds to time = 2 milliseconds) of Signal A is to be studied using an oscilloscope similar to the one used in the lab. Discuss how you would set each of the following settings of the oscilloscope so that an optimum, quantitative display of ~1 milliseconds of the Signal A. Don t forget that a given control might not apply to a particular situation. If so, just mark the control as Not Involved. Don t forget that the settings of several controls go in steps of 1, 2, 5, 1, 2, 5, 1, For thresholds, offsets, etc, give the value in volts of the setting that you wish. a) Channel 1 Input b) Channel 2 Input c) External Input d) Timebase e) Timebase Calibrate f) Channel 1 Sensitivity g) Channel 1 Sensitivity Calibrate h) Channel 1 Offset i) Channel 2 Sensitivity Thursday, October 16,

4 j) Channel 2 Sensitivity Calibrate k) Channel 2 Offset l) Channel1/Both/Channel2 m) Trigger source n) Trigger level o) Trigger slope Thursday, October 16,

5 Question 2. The circuit in Figure 4 has the values: V1 = 15. volts, R1 = 2 kω, R2 = 1 kω, R3 = 12 kω, R4 = 12 kω. What is the value of V2? Show your work. R 1 R 2 V 1 V 2 R 3 R 4 FS3Exam1_DCa.cdr Figure 4 Thursday, October 16,

6 Question 3. For this problem assume that V 1 is a 6 Hz sign wave with a peak-to-peak amplitude of 16 volts. Assume that n p = 16, n 2a = 24, n 2b = 24. FS3Exam1_PS.cdr 13-OCT-23 e f R Pass g i L V 2a V 3 V 4 Control V 5 C R L n sa V 1 n p n sb V 2b Figure 5 - Linear Power Supply a) Sketch the time behavior of V 2a and V 2b. Clearly label your axes and tick marks so that the values of the peak voltages of the signals will be clearly indicated. Thursday, October 16,

7 b) If the circuit in Figure 5 is broken at point e, sketch the time behavior of V 3. Clearly label your axes and tick marks so that the values of the peak voltages of the signals will be clearly indicated. c) What is the function of R PASS and Control? Thursday, October 16,

8 Question 4. a) (1 points) An experiment generates a constant voltage signal, the amplitude of which encodes the value of a parameter of interest. Unfortunately, 6 Hz and 12 Hz noise from the fluorescent lights is added to the signal in the process and conflicts with the measurement of the voltage signal. Discuss how one of the circuits discussed in class can be used to combat this noise. Include the schemat of the circuit and the diagram that relates the input and output of the circuit. b) (5 points) Discuss how you would choose the values of the components to be included in the circuit. You may do this in a qualitative way.. Thursday, October 16,

9 Question 5. Figure 6 illustrates an attempted voltage measurement of a real voltage source that can be modeled as an ideal source, V S, in series with a resistance, R S. The voltage reading is reported by a real voltage meter that can be modeled as an ideal voltage meter that displays the value of e M and has an input resistance, R M, between the inputs. If R 1 = 3KΩ, R 2 = 6K Ω, and R M = 1 MΩ, and e M is observed to be 6. volts, answer the following questions. Assume that i + = i - = for both operational amplifiers, i M+ = i M- =, and both operational amplifiers are operational. R S and V S are unknown. Show your work. FS3Exam1_Loading R 1 R 2 i M i M+ R M + - Ideal VMD i M- Real Voltage Source Figure 6 Real Voltage Measuring Device (VMD) a) What is the value of e 2? Thursday, October 16,

10 b) What is the value of the e 1? c) What is the value of the current is? d) Can a value of V S be determined? Explain your answer. e) Is this a good measurement? Explain. If not, how might it be improved? Thursday, October 16,

11 Question 6. a) (5 points) Sketch the characteristic curve of a diode. Label the axes and the three regions of operation. b) (3 points) What types of diodes should be used in the circuit of Figure 5? c) (4 points) Briefly discuss the operation of either of the diodes in the circuit of Figure 5. d) (3 points) The real diodes in the circuit of Figure 5 limit the amount of current that can be passed to the load. Explain why this is true. Thursday, October 16,

12 Question 7. The following circuit is completed by connecting Q A to X, Q B to Y, and Q C to Z. A periodic pulse train is connected to the input IN. Complete the state table below for the circuit for at least 1 pulses(cycles) of the signal IN. Each line will represents the state of the devices resulting from the nth pulse(cycle) of the signal IN. Note: In some cases there may be more than one step after a given pulse(cycle) of the signal IN and will require multiple lines to describe the sequence of events. Assume that all three flip flops are initially cleared. The flip flops are cleared by a low on the Clear inputs. Extra columns and rows are included for your convenience. You may not need them. A B C Se t Set Set Q Q Q IN Clock Clear _ Q Clock Clear _ Q Clock Clear _ Q X Y CLEARALL Z Figure 7 - Variable Modulo Counter CLEARALL Q C Q B Q After Pulse # A Thursday, October 16,

13 Question 8. Figure 8 is a comparator that is to be treated as ideal and has V OH = 5. volts and V OL =. volts. v x v y v out Figure 8 Comparator Figure 9 shows two cycles of the periodic function Signal D. Signal D is connected to V x of the comparator of Figure 8. A constant voltage of 9. volts is connected to V y. On Figure 1, sketch the resultant output of the comparator (V out ) for the 14 milliseconds shown in Figure 9. Thursday, October 16,

14 15 1 Signal D (volts) Time (milliseconds) Figure 9 - Signal D 15 Comparator Output (volts) Time (milliseconds) Figure 1 - Comparator Output Thursday, October 16,

15 Question 9. A two input NOR gate is to be used to gate a logic signal, A, shown below. The gate control signal, B, is to be constructed so that the gate will be closed except for the intervals t = 5 to t = 12 and t = 2 to t = 23. The output of the gate is to be called M. a.) (3 points) Draw the symbol for the NOR gate and indicate where the signals A, B, and M will be. b.) (4 points) Give the table of states for the NOR gate. B A M c.) (4 points) On the first blank plot provided below, sketch the gate control signal, B, that you would have to supply to achieve the desired gating. d.) (4 points) On the second blank plot provided below, sketch the gate output, M, that would result. Thursday, October 16,

16 A B M Time Thursday, October 16,