Quiz Electrical Engineering

Exam: GATE

Topic: Miscellaneous

Date: 18/06/2021

Each Question carries 2 Mark

Negative Marking: 1/3

Time: 20 Minutes

Q1. If a 220/440 V, 50 Hz, single phase transformer is operated on 220 V, 40 Hz supply then

(a) The eddy current loss and hysteresis loss of the transformer will decrease

(b) The eddy current loss and hysteresis loss of the transformer will increase

(c) The hysteresis loss of the transformer increases while eddy current loss remains the same

(d) The hysteresis loss remains the same, whereas eddy current loss decreases

Q2. A three-phase squirrel cage induction motor has a starting current of seven times the full load current and full load slip of 5%. If an auto transformer is used for reduced voltage starting to provide 1.5 per unit starting torque, the auto transformer ratio (%) should be

(a) 57.77

(b) 72.56%

(c) 78.25%

(d) 81.33%

Q3. A 1:5 step-up transformer has 120 V across the primary and 600 Ω resistance across the secondary. Assuming, 100 % efficiency, the primary current equals…

(a) 5 A

(b) 10 A

(c) 20 A

(d) 0.2 A

Q4. A bipolar transistor has α=0.98, I_CO=10 µA. If the base current is 100 µA, then collector current would be

(a) 4.9 mA

(b) 2.9 mA

(c) 3.4 mA

(d) 5.4 mA

Q5. Two identical unloaded generators are connected in parallel as shown in the figure.

Both the generators are having positive, negative and zero sequence impedance of j0.4 pu, j0.3 pu and j0.15 pu, respectively. If the pre-fault voltage is 1 pu for a line to ground (L-G) fault at the terminals of the generators, the fault current, in pu is………….

(a) 1 pu

(b) 2 pu

(c) 6 pu

(d) 4 pu

Q6. In the circuit shown below, what is the voltage across 5 Ω resistor?

(a) – 30 V

(b) 30 V

(c) 1250 V

(d) – 1250 V

Q7. A DC ammeter has a resistance of 0.1 Ω and its current range is 0-100 A. If the range is to be extended to 0-500 A, the meter requires which of the following shunt resistance?

(a) 0.010 Ω

(b) 0.011 Ω

(c) 0.025 Ω

(d) 1.0 Ω

Q8. The parameters of transposed overhead transmission line are given as:

Self-reactance X_s=0.4 Ω/km

Mutual reactance X_m=0.1 Ω/km

The positive sequence reactance x_1 and zero reactance x_0, respectively in Ω/km are

(a) 0.3, 0.2

(b) 0.5, 0.2

(c) 0.5, 0.6

(d) 0.3, 0.6

Q9. The closed loop transfer function of a control system is given by

C(s)/R(s) =1/((s+1))

For the input r(t)=sint, the steady state value of c(t) is equal to

(a) 1

(b) 1/√2 sint

(c) 1/√2 cost

(d) 1/√2 sin〖(t-π/4)〗

Q10. The eigen-values of the matrix are

(a) 0, 0

(b) 0, a

(c) 0, (a+1)

(d) 0, (a-1)

SOLUTIONS

S7. Ans.(c)

Sol. The range of an ammeter can be easily increased by adding a shunt resistance of very low value to bypass the major part of the current through the resistance path instead of ammeter. This increases the range of an ammeter by reducing the actual current flow through the ammeter.

R_sh=R_m/(m-1)

Where, m is the multiplication factor = 500/100 = 5

∴ R_sh= 0.1/4 = 0.025 Ω.

S8. Ans.(d)

Sol. For transmission line:

positive sequence reactance x_1=x_s-x_m=0.4-0.1=0.3

zero reactance x_0=x_s+2x_m=0.4+0.2=0.6