This set of Instrumentation Transducers Multiple Choice Questions & Answers (MCQs) focuses on “Feedback Transducer System”.
1. Difference between input signal and feedback signal is known as ____________
a) Feedback factor
b) Error signal
c) Output signal
d) Input signal
Explanation: Error signal is the difference between input signal and feedback signal. For a negative feedback loop error signal is given by;
e(t)=xi(t) – xf(t)
2. Error signal in positive feedback system will be ____________ input signal.
a) Greater than
b) Lower than
c) Equal to
d) Negative of
Explanation: In positive feedback signal is added with input signal and obtained error signal.
3. Which of the following represents complete expression for closed loop system?
b) A/ Aβ
c) A/ (1+Aβ)
d) 1/ (1+Aβ)
Explanation: A/ (1+Aβ) represents closed loop gain for negative feedback system, for positive feedback system closed loop gain will be A/ (1+Aβ).
4. Which of the following change have been happened to output impedance in negative feedback system?
c) No change
Explanation: Output impedance with feedback in negative feedback system is given by;
Rof= Ro/ (1+Aβ)
5. Voltage gain improves on application of negative feedback.
Explanation: Voltage gain with feedback network is given by Af= A/ (1+Aβ), In which gain decreased by a factor 1+Aβ.
6. Input impedance ban be _______________ on application of negative feedback.
d) Maintained constant
Explanation: Expression for input impedance on negative feedback is given by Rif=Ro(1+Aβ), in which it is increased by a factor (1+Aβ).
7. For a negative feedback system, A=3 and β=2 and output impedance without feedback is 100Ω. What will be its total output impedance?
a) 14.3 Ω
b) 700 Ω
c) 33.33 Ω
d) 50 Ω
Explanation: Output impedance with feedback in a negative feedback system is
8. Input impedance of a system is 50 Ω, for the system to be negative feedback, which of the following can be its input impedance without feedback?
a) 50 Ω
b) 60 Ω
c) 40 Ω
d) 100 Ω
Explanation: For a negative feedback system input impedance increases after feed backing.
9. In a feedback gain equation, what does the term β stands for?
a) Feedback gain
b) Forward gain
c) Open loop gain
d) Closed loop gain
Explanation: The term β stands for feedback gain and it is the gain of feedback system only.
10. In which of the following conditions, feedback gain (Af) become independent of forward gain (A)?
Explanation: Expression for feedback gain in negative feedback loop is given by;
Af= A/ (1+Aβ)
In which, when Aβ>>1, Af becomes reciprocal of loop gain β.
Sanfoundry Global Education & Learning Series – Instrumentation Transducers.
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