Quiz: Electrical Engineering 9 Sep 2020

Quiz: Electrical Engineering
Exam: SSC JE
Topic: Miscellaneous

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

Q1. In a power plant if the maximum demand on the plant is equal to the plant capacity then
(a) Load factor will be nearly 60%
(b) Plant reserve capacity will be zero
(c) Diversity Factor will be unity
(d) Load factor will be unity

Q2. For the circuit shown in figure, the voltage across the capacitor during steady state condition is

(a) 0 V
(b) 4 V
(c) 6 V
(d) 12 V

Q3. Find R_AB for the circuit shown in figure.

(a) 18Ω
(b) 30Ω
(c) 45Ω
(d) 68Ω

Q4. A supply voltage of 230 V, 50 Hz is fed to a residential building. Write down its equation for instantaneous value.
(a) 163 sin 314·16 t
(b) 230 sin 314·16 t
(c) 325 sin 314·16 t
(d) 361sin314·16 t

Q5. The AC bridge used for measurement of dielectric loss of capacitor is
(a) Anderson bridge
(b) Schering bridge
(c) Wien bridge
(d) Hay’s bridge

Q6. In a transformer, Low voltage windings are placed nearer to the core in the case of concentric windings because
(a) it reduces hysteresis loss
(b) it reduces eddy current loss
(c) it reduces insulation requirement
(d) it reduces leakage fluxes

Q7. Emf induced in the dc generator armature winding is
(a) AC
(b) DC
(c) AC and DC
(d) None of the above

Q8. In a dc machine 72 number of coils are used. Find the number of commutator segments required?
(a) 72
(b) 36
(c) 37
(d) 74

Q9. Reactance relay is used for protection in:
(a) Long transmission lines
(b) Short transmission lines
(c) Medium transmission lines
(d) Both long transmission lines and short transmission lines

Q10. The earthing electrode should be situated at a place at least ………. meters away from the building whose installation system is being earthed?
(a) 4
(b) 2.5
(c) 1.5
(d) 0.5

SOLUTIONS
S1. Ans.(b)
Sol. Reserve capacity = Plant capacity – Max. Demand
If the plant capacity is equal to Max. Demand then the Reserve capacity will be zero.

S2. Ans.(d)
Sol. under steady state condition, capacitor behaves as open circuit. So, source voltage will appear across the capacitor.
So, voltage across capacitor during steady state= 12 V

S3. Ans.(a)
Sol. given circuit is a balanced bridge.
So, RAB=(20+10)‖ |(30+15)=(30×45)/75=18 Ω

S4. Ans.(c)
Sol. V=Vm sin⁡(2πft)=230×√2 sin⁡(2×3.14×50 t)=325 sin⁡(314.16 t)

S5. Ans.(b)
Sol. Schering bridge is used for measurement of dielectric loss of capacitor.

S6. Ans.(c)
Sol. In concentric arrangement of placing of HV and LV winding, less insulation is required when LV winding is placed near the core which is at ground potential. The HV winding is placed around the LV.
If high voltage winding is placed near the core, the more insulation will be required and the more insulation lead to increase in the size and cost of the transformer.

S7. Ans.(a)
Sol. The emf induced in the dc generator armature winding is AC, but we need DC current from DC generator, so to convert this AC current to DC current mechanical rectifier called as commutator is used.

S8. Ans.(a)
Sol. In DC machines, Number of coils = Number of commutator segments.

S9. Ans.(b)
Sol. Relay used for different configuration of transmission lines……
Short transmission line: reactance relay
Medium transmission line: impedance relay
Long transmission line: mho relay

S10. Ans.(c)
Sol. The earthing electrode should be situated at a place at least 1.5 meters away from the building whose installation system is being earthed
The earthing electrode should always be placed in a vertical position inside the earth or pit so that it may be in contact with all the different earth layers.

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