Electronics Engineering - Online Test
Q1. 
The Nyquist plot of a stable transfer function G(s) is shown in the figure are interested in the stability of the closed loop system in the feedback configuration shown.
Which of the following statements is true ?
Answer : Option B
Explaination / Solution:
The plot has one encirclement of origin in clockwise direction. Thus G(s) has a zero is in RHP.
Q2. In the circuit shown below, the initial charge on the capacitor is 2.5 mC, with
the voltage polarity as indicated. The switch is closed at time t = 0. The current i(t) at a time t after the switch is closed is
Answer : Option A
Explaination / Solution:
Here we take the current flow direction as positive.
Q3. The output of the combinational circuit given below is
Answer : Option C
Explaination / Solution:
Q4. 
The Nyquist plot of a stable transfer function G(s) is shown in the figure are interested in the stability of the closed loop system in the feedback configuration shown.
The gain and phase margins of G(s) for closed loop stability are
Answer : Option C
Explaination / Solution:
The Nyzuist plot intersect the real axis ate - 0.5. Thus
G. M. =- 20 log x =- 20 log 0.5 = 6.020 dB
And its phase margin is 90◦c
Q5. A network consisting of a finite number of linear resistor (R), inductor (L), and capacitor (C)
elements, connected all in series or all in parallel, is excited with a source of the form
The source has nonzero impedance. Which one of the following is a possible form of the
output measured across a resistor in the network?
Answer : Option A
Explaination / Solution:
The property of any LTI system or network is if the excitation contains „n‟ number of different
frequency then the response also contains exactly n number of different frequency term and the
output frequency and input frequency must be same however depending on components there
is a possible change in amplitude and phase but never the frequency.
⟶ If the source has 3 frequency terms as given 
then any voltage or any current of any element should have also 3 terms based on this option (B) and (D) are eliminated.
then any voltage or any current of any element should have also 3 terms based on this option (B) and (D) are eliminated.⟶ If we take option (C). It has 3 frequency term but it also suggest there is a phase change so ϕk but amplitude must be same as input as ak is present which may not be true always.
⟶ So option (A) is correct, as it suggest frequency term of output and inputs are same with
possible change in amplitude and phase, because we have (bk and ϕk ).
Q6. Identify the circuit below.
Answer : Option A
Explaination / Solution:
No Explaination.
Q7. The Bode plot of a transfer function G(s) h is shown in the figure below.
The gain (20 log ƖG(S)Ɩ) is 32 dB and -8 dB at 1 rad/s and 10 rad/s respectively The phase is negative for all ω Then G(S) is
Answer : Option B
Explaination / Solution:
From the given plot, we obtain the slope as
Q8. The functionality implemented by the circuit below is
Answer : Option B
Explaination / Solution:
Decoder inputs will behaves as MUX select lines and when the output of decoder is high then only corresponding buffer will be enable and passed the inputs (P,Q,R,S) to the outpuut line, so it will work as 4-to-1 multiplexer.
Q9. In the circuit shown below, if the source voltage 
then the
Thevenin’s equivalent voltage in Volts as seen by the load resistance RL is
then the
Thevenin’s equivalent voltage in Volts as seen by the load resistance RL is
Answer : Option C
Explaination / Solution:
No Explaination.
Q10.
In a voltage-voltage feedback as shown below, which one of the following statements is TRUE if the gain k is increased?
Answer : Option A
Explaination / Solution:
The i/p voltage of the system is given as
Therefore, if k is increased then input voltage is also increased so, the input impedance increases. Now, we have
Since, Vin is independent of k when seen from output mode, the output voltage decreases with increase in k that leads to the decrease of output impedance. Thus, input impedance increases and output impedance decreases.
