Electronics Engineering - Online Test
Q1. 
For the discrete-time system shown in the figure, the poles of the system transfer function are located at
Answer : Option C
Explaination / Solution:
We have the discrete time system as shown in figure below.
The circuit is minimized as
Hence, poles are at
z = 1/2, 1/3
Q2. The built-in potential of the junction
Answer : Option B
Explaination / Solution:
We know that
Q3.
For 8085 microprocessor, the following program is executed.
MVI A, 05H;
MVI B, 05H;
PTR: ADD B;
DCR B;
JNZ PTR;
ADI 03H;
HLT;
At the end of program, accumulator contains
Answer : Option A
Explaination / Solution:
The program is being executed as follows
MVI A, 0.5H; A = 05H
MVI B, 0.5H; B = 05H
At the next instruction, a loop is being introduced in which for the instruction “DCR B” if the result is zero then it exits from loop so, the loop is executed five times as follows :
i.e., A = 05 + 05 + 04 + 03 + 02 + 01 = 144
At this stage, the 8085 microprocessor exits from the loop and reads the next instruction. i.e., the accumulator is being added to 03 H. Hence, we obtain A = A + 03 H = 14 + 03 = 17 H
Q4. Which one of the following is an eigen function of the class of all continuous-time, linear, time-invariant systems u(t) denotes the unit-step function)?
Answer : Option C
Explaination / Solution:
No Explaination.
Q5. Two magnetically uncoupled inductive coils have Q factors q1 and q2 at the
chosen operating frequency. Their respective resistances are R1 and R2. When
connected in series, their effective Q factor at the same operating frequency is
Answer : Option C
Explaination / Solution:
The quality factor of the inductances are given by
So, in series circuit, the effective quality factor is given by
Q6. A plant transfer function is given as 
When the plant operates in a unity feedback configuration, the condition for the stability of the closed loop system is
When the plant operates in a unity feedback configuration, the condition for the stability of the closed loop system is
Answer : Option A
Explaination / Solution:
Given plant transfer function,
So, closed loop transfer function is
Therefore, characteristics equation is
For stability, we form the Routh array.
For stability, we must have
Q7.
Consider a delta connection of resistors and its equivalent star connection as shown below. If all elements of the delta connection are scaled by a factor k, k > 0, the elements of the corresponding star equivalent will be scaled by a factor of
Answer : Option B
Explaination / Solution:
In the equivalent star connection, the resistance can be given as
Q8. The output Y in the circuit below is always ‘1’ when
Answer : Option B
Explaination / Solution:
The given circuit is shown below:
If any two or more inputs are ‘1’ then output y will be 1.
Q9. A continuous-time function x(t) is periodic with period T. The function is sampled uniformly
with a sampling period TS. In which one of the following cases is the sampled signal periodic?
Answer : Option B
Explaination / Solution:
Q10. 
The pole-zero diagram of a causal and stable discrete-time system is shown in the figure. The zero at the origin has multiplicity 4. The impulse response of the system is h[n]. If h[0] = 1, we can conclude
Answer : Option A
Explaination / Solution:
From the pole-zero plot, we obtain the transfer function as
