Electrical Engineering - Online Test
Q1. The voltage gain Av of the circuit shown below is
Answer : Option D
Explaination / Solution:
Q2. The flux density at a point in space is given by 
The value of constant k must be equal to
The value of constant k must be equal to
Answer : Option A
Explaination / Solution:
No Explaination.
Q3. The DC current gain (β) of a BJT is 50. Assuming that the emitter injection
efficiency is 0.995, the base transport factor is
Answer : Option B
Explaination / Solution:
Q4.
Group I lists four different semiconductor devices. match each device in Group I with its charactecteristic property in Group II
Group-I Group-II
(P) BJT (1) Population iniversion
(Q) MOS capacitor (2) Pinch-off voltage
(R) LASER diode (3) Early effect
(S) JFET (4) Flat-band voltage
Answer : Option C
Explaination / Solution:
In BJT as the B-C reverse bias voltage increases, the B-C space charge region
width increases which xB (i.e. neutral base width) > A change in neutral base
width will change the collector current. A reduction in base width will causes
the gradient in minority carrier concentration to increase, which in turn causes
an increased in the diffusion current. This effect si known as base modulation as
early effect.
In JFET the gate to source voltage that must be applied to achieve pinch off
voltage is described as pinch off voltage and is also called as turn voltage or
threshold voltage.
In LASER population inversion occurs on the condition when concentration of
electrons in one energy state is greater than that in lower energy state, i.e. a non
equilibrium condition.
In MOS capacitor, flat band voltage is the gate voltage that must be applied to
create flat ban condition in which there is no space charge region in semiconductor
under oxide.
Therefore
BJT : Early effect
MOS capacitor : Flat-band voltage
LASER diode : Population inversion
JFET : Pinch-off voltage
Q5. A point Z has been plotted in the complex plane, as shown in figure below.
The plot of the complex number y = 1/z is
Answer : Option D
Explaination / Solution:
Z is having +ve real part and positive imaginary part (from the characteristics) So Y should have +ve real part and negative imaginary part.
Q6. Given two continuous time signals 
which exist for t > 0,
the convolution z(t) = x(t)* y(t) is
which exist for t > 0,
the convolution z(t) = x(t)* y(t) is
Answer : Option A
Explaination / Solution:
Q7. The raised cosine pulse p(t) is used for zero ISI in digital communications. The
expression for p(t) with unity roll-off factor is given by
The value of p(t) at t = 1/W is
Answer : Option C
Explaination / Solution:
Q8. A lossy capacitor Cx, rated for operation at 5 kV, 50 Hz is represented by an
equivalent circuit with an ideal capacitor Cp in parallel with a resistor Rp. The
value Cp is found to be 0.102 µF and the value of Rp = 1.25 MΩ . Then the power
loss and tan ∂ of the lossy capacitor operating at the rated voltage, respectively,
Answer : Option C
Explaination / Solution:
No Explaination.
Q9. A 220 V, DC shunt motor is operating at a speed of 1440 rpm. The armature
resistance is 1.0 Ω and armature current is 10A. of the excitation of the machine
is reduced by 10%, the extra resistance to be put in the armature circuit to
maintain the same speed and torque will be
Answer : Option A
Explaination / Solution:
Q10. 
A load center of 120MW derives power from two power stations connected by 220kV transmission lines of 25km and 75km as shown in the figure below. The three generators G1,G2 and G3 are of 100MW capacity each and have identical fuel cost characteristics. The minimum loss generation schedule for supplying the 120 MW load is
Answer : Option A
Explaination / Solution:
Loss α p2 ; Loss α length
For checking all options only option A gives less losses.
