Electronics Engineering - Online Test
Q1. The input and output of a continuous time system are respectively denoted by x(t) and y(t). Which of the following descriptions corresponds to a causal system ?
Answer : Option C
Explaination / Solution:
The output of causal system depends only on present and past states only.
In option (A) y(0) depends on x(- 2) and x(4).
In option (B) y(0) depends on x(1).
In option (C) y(0) depends on x(- 1).
In option (D) y(0) depends on x(5).
Thus only in option (C) the value of y(t) at t = 0 depends on x(- 1) past value.
In all other option present value depends on future value.
Q2. Drift current in the semiconductors depends upon
Answer : Option C
Explaination / Solution:
No Explaination.
Q3. 
For the output F to be 1 in the logic circuit shown, the input combination should be
Answer : Option C
Explaination / Solution:
Q4. In the circuit shown, vC is 0 volts at t = 0 sec. For t > 0, the capacitor current iC(t), where t is in seconds is given by
Answer : Option A
Explaination / Solution:
Q5.
The longitudinal component of the magnetic field inside an air-filled rectangular waveguide made of a perfect electric conductor is given by the following expression 
The cross-sectional dimensions of the waveguide are given as a = 0.08 m and b = 0.033 m. The mode of propagation inside the waveguide is
The cross-sectional dimensions of the waveguide are given as a = 0.08 m and b = 0.033 m. The mode of propagation inside the waveguide is
Answer : Option C
Explaination / Solution:
We have the expression,
and the cross sectional dimension is
a = 0.08 m, b = 0.033m
Now, we compare the equation for TEm,n mode whose Hz is given as
Hence, given mode is TE21 mode
Q6. The impulse response h(t) of a linear time invariant continuous time system is
described by 
where u(-t) denotes the unit
step function, and α and β are real constants. This system is stable if
where u(-t) denotes the unit
step function, and α and β are real constants. This system is stable if
Answer : Option D
Explaination / Solution:
This system is stable only when bounded input has bounded output For stability αt < 0 for t > 0 that implies α < 0 and βt > 0 for t > 0 that implies β > 0. Thus, α is negative and β is positive.
Q7. The pole-zero given below correspond to a
Answer : Option C
Explaination / Solution:
Q8. A Zener diode, when used in voltage stabilization circuits, is biased in
Answer : Option B
Explaination / Solution:
Zener diode operates in reverse breakdown region.
Q9. In the circuit shown, the device connected Y5 can have address in the range
Answer : Option B
Explaination / Solution:
Q10. In the ac network shown in the figure, the phasor voltage VA (in Volts) is
Answer : Option D
Explaination / Solution:
