Quiz: Electrical Engineering 10 June 2020

Quiz: Electrical Engineering
Topic: Miscellaneous

Each question carries 1 mark.
Negative marking: 1/4 mark
Time: 10 Minute

Q1. A 3-phase 4- wire system is commonly used for
(a) primary distribution
(b) secondary distribution
(c) primary transmission
(d) secondary transmission

Q2. Which of the following is usually not the generating voltage?
(a) 6.6 kV
(b) 9.9 kV
(c) 11 kV
(d) 13.2 kV

Q3. The main drawbacks of overhead transmission system over underground system is/are
(a) underground system is more flexible than overhead system
(b) higher charging current
(c) surge problem
(d) high initial cost

Q4. Improving pf
(a) reduces current for a given output
(b) increases losses in line
(c) increase the cost of station equipment
(d) none of the above

Q5. DC motors are still preferred for use in
(a) electric excavators
(b) lathes and machine tools
(c) floor mills and jaw crusher
(d) paper industry

Q6. The least significant feature while selecting a motor for centrifugal pump is
(a) speed control
(b) power rating of motor
(c) operating speed
(d) starting characteristic

Q7. BCD code is
(a) a binary code
(b) unweighted code
(c) the same thing as binary number
(d) the same as gray code

Q8. A unit impulse response of a second order system is 1/6 e^(-0.8t) sin (0.6t). Then natural frequency and damping ratio of the system are
(a) 1 and 0.6
(b) 1 and 0.8
(c) 2 and 0.4
(d) 2 and 0.3

Q9. Damping ratio ξ and peak overshoot M_p are measure of
(a) relative stability
(b) absolute stability
(c) speed of response
(d) steady state error

Q10. For a critically damped system, the closed-loop poles are
(a) purely imaginary
(b) real, equal and negative
(c) complex conjugate with negative real part
(d) real unequal and negative

S1. Ans. (b)
Sol. A 3-phase 4- wire system is commonly used for secondary distribution.

S2. Ans. (b)
Sol. 9.9 kV is usually not the generating voltage.

S3. Ans. (c)
Sol. Surge problem is only advantage of overhead transmission system.

S4. Ans. (a)
Sol. Since Power, P = VI cos φ , cos φ (power factor)
If cos φ will improve for a given output the value of current will decrease.
S5. Ans. (a)
Sol. electric excavators

S6. Ans. (a)
Sol. speed control

S7. Ans. (a)
Sol. BCD code is a binary code

S8. Ans. (b)
Sol. h (t) = 1/6 e^(-0.8t) sin (0.6t)
On comparing it with the standard equation,
i.e. Ke^(-ξω_n t)/√(1-ξ^2 ) sin⁡〖(ω_d t+ Ǿ)〗
we have, ξω_n=0.8 …………………………. (i)
ω_d= ω_n √(1-ξ^2 )
= 0.6 rad/sec ……………………. (ii)

Solving both equation
ω_n=1 rad/sec and 𝞷 = 0.8

S9. Ans. (c)
Sol. speed of response

S10. Ans. (b)
Sol. real, equal and negative


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