# Electrical Engineering test questions for exams and entrance - 3

## Electrical Engineering test questions for exams and entrance - 3

(1) An input device whose address is 2500H is interfaced with Intel 8085A microprocessor as memory mapped I/O. Which is the correct sequence of instructions to input the data from the

device to accumulator?

(A) LHLD 2500H
MOV M, A
(B) LHLD 2500H
MOV A, M
(C) LXI H, 2500H
MOV M, A
(D) LXI H, 2500H
MOV A, M

MOV A, M

(2) We have the third order equation whose first two rows of Routh’s tabulation are
as follows

S³ 2 2
S³ 4 4

This means that there are

(A) Two roots at s = ± j and one root in the right half of s plane
(B) Two roots at s = ± j and one root in the left half of s plane.
(C) Two roots at s = ± j2 and one root in the right half of s plane
(D) Two roots at s = ± j2 and one root in the left half of s plane

ANSWER: Two roots at s = ± j and one root in the left half of s plane.

(3) The rms value of a zero mean random signal, which is uniformly distributed between limits –α and +α and whose mean square value is equal to its variance is

(A) a
(B) a/√2
(C) a/√3
(D) 2a

(4) An ammeter whose internal resistance is 0.2Ω has current range of 0-5A. Which resistance is to be added in order to change the range to 0-25A?

(A) 0.05Ω in parallel with the meter.
(B) 0.2Ω in parallel with the meter
(C) 0.05Ω in series with the meter
(D) 1Ω in series with the meter

ANSWER: 0.05Ω in parallel with the meter.

(5) When two systems whose impulse response h1 (t) and h2 (t) are connected in cascade then the overall impulse response is given by

(A) Summation of h1 (t) and h2 (t)
(B) Product of h1 (t) and h2 (t)
(C) Subtraction of h1 (t) and h2 (t)
(D) Convolution of h1 (t) and h2 (t)

ANSWER: Convolution of h1 (t) and h2 (t)

(6) Consider a 4 ½ digit DMM that has the error specification as 0.2% of reading +10 counts. What will be the maximum error that can be expected in the reading, if a dc voltage of 100v is

read on its 200v full scale?

(A) ±0.2%
(B) ±0%
(C) ± 0.3%
(D) ±0.1%

(8) The impedance parameters (z, z12, z21, z22) of i1 = 2v1 + v2 and i2 = v1 + v2 that define a two-port device are

(A) (2, 1, 1, 1)
(B) (1, -1, -1, 2)
(C) (2, 1, -1, 1)
(D) (-1, 1, 1, 2)

(9) Let Y be the square matrix. Y will be Skew Hermitian if and only if

(A) Y° = -Y
(B) Y° = 0
(C) Y° = 1
(D) Y° = Y

(10) The reason to consider an SCR as a semi-controlled device is that

(A) It can be turned ON but not OFF with a gate pulse.
(B) It can be turned OFF but not ON with a gate pulse.
(C) It can be turned ON only during one half cycle of an alternating voltage wave.
(D) None of the above reasons are valid.

ANSWER: It can be turned ON but not OFF with a gate pulse.

For questions 11 and 12 refer to the data given below:

Consider a 1-phase transformer having 2200/220V, 50 Hz rating. The emf per turn of the transformer is approximately 12 V.

(11) What will be the secondary turns?

(A) 19
(B) 11
(C) 15
(D) 18

(12) For maximum flux density of 1.5T, the net cross-sectional area of core is

(A) 0.122 m²
(B) 0.092m²
(C) 0.036 m²
(D) None of the above

(13) A 20 Km long underground cable has insulation resistance of 8MΩ. What will be the insulation resistance of 10Km long cable keeping other things same.?

(A) 1MΩ
(B) 5MΩ
(C) 16MΩ
(D) 8MΩ

(14) Amplitude of electric field corresponding to the incoming solar radiation of 1.2KW/m² at a place on the surface of the earth is nearly equal to.

(A) 950 V/m
(B) 1000 V/m
(C) 420 V/m
(D) 220 V/m

(15) Shift register ceases to work as a shift register in _________ mode of operation.

(A) SIPO
(B) PIPO
(C) PISO
(D) SISO

(16) In a compensated op-amp, the first dominant pole encountered in the frequency response is approximately at

(A) 10Khz
(B) 100Mhz
(C) 1Hz
(D) 5Hz

Questions 17 and 18 are linked:

(17) What will be the progressive phase shift that can be applied to the elements?

(A) π/4
(B) π/6
(C) π/2
(D) None of the above

(18) For this phase distribution, the angle at which main beam is placed is

(A) 120°
(B) 60°
(C) 180°
(D) 90°

(19) If input voltage is maintained constant at the rated value corresponding to 50 Hz, can a 50 Hz transformer be used as 25 Hz?

(A) Yes
(B) No
(C) Depends on circuit parameters
(D) Depends on external input.

(20) In the output stage of TTL gate, Darlington emitter-follower circuit is sometimes used to

(A) Reduce power dissipation
(B) Increase its speed of operation
(C) Decrease its speed of operation
(D) Increase its current flow

ANSWER: Increase its speed of operation

(22) Let us consider that a slightly unbalanced 3-phase, 50 Hz source is supplied to a 4-pole induction motor and the motor is rotating at 1440rpm. What will be the electrical frequency of

the induced negative sequence current in the rotor?

(A) 25Hz
(B) 50Hz
(C) 98Hz
(D) 100Hz

(23) The equation f(x) = x³ + 2x – 1 = 0 is solved by using Newton-Raphson method. With the initial guess as xo = 1.2, the solution at the end of first iteration is

(A) 1.980
(B) 0.705
(C) -0.598
(D) 0.655

For Questions 24 and 25 refer to the data given below:

Figure is the linear nonreciprocal two-port network. When 10v dc is connected at port A, following were observed:

i) Current drawn is of 3 A when 1 ohm resistance is connected at port B.
ii) Current drawn is of 2 A when 2.5 ohm resistance is connected at port B.

(24) When 6V dc is connected at port A and 1ohm resistance is connected at port B, the current drawn is 7/3 A. When 8V dc is connected at port A, the open circuit voltage at port B will be
(A) 1V
(B) 5V
(C) 10V
(D) 8V

(25) When 10V dc is connected at port A and 7ohm resistance is connected at port B, the current drawn by 7ohm resistance will be

(A) 3A
(B) 1A
(C) 1/3A
(D) 2/9A