Quiz: Electrical Engineering 01 Oct 2020

Quiz: Electrical Engineering
Exam: RSMSSB-JEn
Topic: Miscellaneous

Each question carries 1 mark.
Negative marking: 1/3 mark
Time: 10 Minute

Q1. The rotor of which motor does not have winding on it?
(a) Repulsion motor
(b) Universal motor
(c) Reluctance motor
(d) Hysteresis motor

Q2. The ratio of starting torque to running torque in a synchronous motor is:
(a) 0
(b) 1
(c) 2
(d) ꝏ

Q3. The torque-slip characteristics of a polyphase induction motor becomes almost linear at small value of slip, because in this region of slips:
(a) The effective rotor resistance is very large compared to the rotor reactance.
(b) The effective rotor resistance is very small compared to the rotor reactance.
(c) The effective rotor resistance is equal to the rotor reactance.
(d) The effective rotor resistance is equal to the stator reactance.

Q4. A shunt reactor of 100 MVAR is operated at 98% of its rated voltage and at 96% of its rated frequency. What is the reactive power absorbed by the reactor?
(a) 98 MVAR
(b) 104.02 MVAR
(c) 96.04 MVAR
(d) 100.04 MVAR

Q5. A dielectric material is placed in vacuum in a uniform electric field of E = 4 V/m. what is the electric field inside the material if the relative permittivity of dielectric material is 2?
(a) 0 V/m
(b) 2 V/m
(c) 4 V/m
(d) 8 V/m

Q6. A spring controlled moving iron voltmeter draws a current of 1 mA for full scale value of 100 V. If it draws a current of 0.5 mA, what is the meter reading?
(a) 25 V
(b) 50 V
(c) 100 V
(d) 200 V

Q7. Candela is a unit of:
(a) Luminous intensity
(b) Frequency
(c) Lamp efficiency
(d) Power

Q8. The gas filled in vacuum filament lamps is:
(a) Nitrogen
(b) Chlorine
(c) Argon
(d) Air

Q9. Total core loss is also referred as
(a) Eddy current loss
(b) Hysteresis loss
(c) Copper loss
(d) Magnetic loss

Q10. The primary to secondary turn ratio of a transformer is 1:2. If the primary is connected to 50 Hz supply, then the frequency of secondary supply in Hz is:
(a) 25
(b) 50
(c) 100
(d) 150

SOLUTIONS
S1. Ans.(d)
Sol. A Hysteresis Motor is a synchronous motor with a uniform air gap and without DC excitation.
The rotor of the motor is made up of smooth chrome steel cylinder and it has no winding.

S2. Ans.(a)
Sol. when supply is given to stator starts rotating and stator poles too rotate at synchronous speed. these poles interchange their position due to alternating nature of current. the rotor cannot pick up the quick reversal of stator. Due to this clockwise and counter clockwise directions of torque will develop making average torque zero.

S3. Ans.(a)
Sol. The torque-slip characteristics of a polyphase induction motor becomes almost linear at small value of slip, i.e. X2/R2 ≪1.

S4. Ans.(d)
Sol. The reactive power is given as


∴Q2=100.04 MVAR

S5. Ans.(b)
Sol. D1n=D2n
⇒ϵr1 E1n=ϵr2 E_2n
Where, ϵr1=relative permitivity of vaccum=1
And ϵr2=relative permitivity of medium=2
∴E2n=(1×4)/2=2 V/m

S6. Ans.(a)
Sol. For moving iron meter
Reading ∝ I^2
∴V2/V1 =(I2^2)/(I1^2 )
⇒V2=100×0.25=25 V

S7. Ans.(a)
Sol. Candela is a unit of Luminous intensity.

S8. Ans.(c)
Sol. Argon gas is used in fluorescent and incandescent light bulbs to stop the oxygen in the light bulbs from corroding the hot tungsten filament. The use of argon in lightbulbs prevents the evaporation of the tungsten filaments, which results in increased light bulb life.

S9. Ans.(d)
Sol. Core loss consisting of eddy current loss and hysteresis loss.
i.e. core loss= eddy current loss+ hysteresis loss.
Core loss is mainly due to magnetic properties. So, core loss is also called magnetic loss.
Copper loss is due heat generated due to resistance of winding.

S10. Ans.(b)
Sol. A Transformer is a static electrical machine which transfers AC electrical power from one circuit to the other circuit at the constant frequency, but the voltage level can be altered that means voltage can be increased or decreased according to the requirement.

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