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1. What would be the time constant in an RC circuit when R 200 k and C 10 F? A. 20 sec C. 2 sec B. 5 sec D. 0.5 sec 2. Which of the output waveforms is correct for the input signal shown? A. B. C. D. Pulse Circuits Examination Examination When you feel confident that you have mastered the material in this study unit, complete the following examination. Then submit only your answers to the school for grading, using one of the examination answer options described in your “Test Materials” envelope. Send your answers for this examination as soon as you complete it. Do not wait until another examination is ready. Questions 1–25: Select the one best answer to each question. EXAMINATION NUMBER 2708A Whichever method you use in submitting your exam answers to the school, you must use the number above. For the quickest test results, go to http://www.pennfoster.edu 6 Examination 3. When a pulse is amplified in a linear amplifier, the charge carrier transmit time can cause A. loss of the d-c reference levels. B. rise-time distortion. C. waveform tilt. D. propagation delay. 4. It requires 5 time divisions for a pulse to go from 10% to 90% of full amplitude. The sweep of the scope is calibrated so that 10 sec are represented by 20 divisions. What is the rise time of the pulse? A. 0.25 sec C. 10 sec B. 2.5 sec D. 15 sec 5. In a certain LR time constant circuit, it takes 135 msec for the current to reach maximum after the switch is closed. If the inductance is 4 henrys, what is the value of circuit resistance? A. 670 C. 0.670 B. 148 D. 0.148 6. When you increase the width of a pulse, you A. decrease average value. C. increase overshoot. B. decrease duty cycle. D. increase RMS value. 7. Which of the following will most likely cause arcing at the switch contacts? A. A switch that starts current flowing in an LR time constant circuit B. A switch that opens an LR time constant circuit C. A switch that starts the capacitor charge in an RC time constant circuit D. A switch—that opens an R-b’-time constant circuit fer ihe capacitor to discharge 8. In a certain circuit the output signal is NOT permitted to exceed a certain value even though the input signal tries to drive it beyond that value. What is the circuit? A. Limiter C. Baseline stabilizer B. Clipper D. Ringing oscillator 9. How would you describe a differentiator? A. An RC circuit where the time constant is greater than 1. B. An RC circuit where the time constant is equal to 1. C. A circuit that has an output signal proportional to the sum of input pulses. D. A circuit that has an output signal proportional to the rate of change of the input signal. Examination 7 10. Of the following devices, which one is most suitable for frequency domain displays? A. Memory scope C. Spectrum analyzer B. Oscillograph D. Triggered sweep scope 11. An NPN common emitter transistor, when operated without d-c bias, can be used as a A. d-c restorer. C. positive peak clipper. B. negative peak clipper. D. baseline stabilizer. 12. The amplifier circuit shown uses an enhancement-type N-channel MOSFET. The input signal goes from a slightly positive value to a negative value, then back to a slightly positive value. Which waveform is correct for the output signal? A. B. C. D. 13. What is the bandwidth of an amplifier that produces a square wave with a rise time of 2 sec? A. 20 kHz C. 70 kHz B. 57 kHz D. 175 kHz 14. An advantage of direct-coupled amplifiers is that they A. make ideal clippers. B. make ideal limiters. C. can amplify a signal without inverting it. D. can amplify a signal without changing its d-e reference level. 8 Examination 15. Determine the duty cycle for the pulse shown below. A. 9% B. 23% C. 27% D. 80% 16. When a pulse is delivered to an amplifier, ringing may occur if A. the amplifier is overdriven. B. direct coupling is used. C. there is inductance in the output circuit. D. the amplifier is operated without bias. 17. To transmit only portions of an input wave lying on one side of an amplitude boundary, you would use a A. toggled flip flop. C. limiter. B. d-e restorer. D. clipper. 18. When working with pulse generators, you should be aware that a monostable multi, vibrator is also a(n) A. collector-coupled multivibrator. C. astable multivibrator. B. one-shot multivibrator. D. bilateral compressor. 19. How long will it take for the current to reach 36.7% of its initial value in an inductive discharge circuit if R equals 1000 n and L equals 4 henrys? A. 40 sec C. 0.004 sec B. 10 sec D. 0.001 sec 20. An oscilloscope grid is calibrated so that one square represents 1-V vertically and 1 msec horizontally. If the height of a square wave pulse display is 6 squares, the width of the pulse is 7 squares, and the cycle of the wave is 16 squares, the average value of the pulse is A. 1.73 V. C. 3.97 V. B. 2.63 V. D. 4.32 V. Examination 9 21. To change the relationship between a waveform and the zero-volt axis, and at the same time retain the shape of the wave, you would use a A. toggled flip flop. C. limiter. B. d-e restorer. D. clipper. 22. Which one of the following actions will you take to decrease the rise time of pulses passing through an amplifier? A. Increase low-frequency response. B. Decrease low-frequency response. C. Increase high-frequency response. D. Decrease high-frequency response. 23. The simplest clamping circuit consists of a A. diode and capacitor. C. capacitor and resistor. B. diode and resistor. D. capacitor and inductor. 24. If the pulse repetition rate (PRR) of a transmitted pulse is 400 pulses per second, what is the period of the waveform? A. 2.5 msec C. 25 msec B. 4.0 msec D. 40 msec 25. The time that it takes for a capacitor to completely charge or discharge is, for all practical purposes, equal to ______ time constants. A. two C. four B. three D. five