Haryana Staff Selection Commission (HSSC) Junior Engineer(JE) Electrical 2018 Questions With YouTube Explanation & PDF Part One
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Question-1.Long distance railways operate on
(1) 600 V dc.
(2) 25 kV single phase ac.
(3) 25 kV three phase ac.
(4) 15 kV three phase ac.
Answer-2
Explanation-Railway electrification systems using alternating current (AC) at 25 kilovolts (kV) are used worldwide, especially for high-speed rail and long distance.
Question-2.The speed-time curve for urban service has no
(1) coasting period
(2) free running period
(3) breaking period
(4) acceleration period
Answer-2
Explanation-Urban Service or City Service
• In this service the distance between the stops is comparatively very short. (say 1 km or so)
• Time required for this run is very small.
• The acceleration as well as retardation is required to be high so that high average speed and short time run is obtained.
• Free run is not possible.
• Coasting period is also small.
Speed–Time curve for Urban Service
Question-3.The normal value of co-efficient of adhesion is
(1) 0.25
(2) 0.30
(3) 0.50
(4) 0.65
Answer-3
Explanation-
Coefficient of Adhesion in Traction (μa)=Maximum tractive effort that can be applied without slipping of wheels/Weight on driving excel
Normal value of co-efficient of adhesion is 0.25
Question-4.The voltage required to pass the necessary current through an electrolytic cell is of the order of
(1) 1-2 V
(2) 100-120 V
(3) 10-20 V
(4) 150-200 V
Answer-3
Explanation-The voltage required to pass the necessary current through an electrolytic cell is of the order of 10-20 V.
Question-5.What is the maximum load that is usually connected in a power sub-circuit
(1) 1000 W
(2) 2000 W
(3) 3000 W
(4) 4000 W
Answer-3
Explanation-Power sub-circuit-The load connected in a power sub-circuit normally should not exceed 3,000 watts and the number of outlasts connected on each sub circuit in no case should exceed two.
Single phase 15A sub-circuits (power sub-circuits) are used for connecting heaters, stoves, electric iron, small single phase motors etc.
Question-6.What type of starter will you recommend for a 20 kW squirrel cage induction motor
(1) Auto-transformer starter
(2) D-O-L starter
(3) Star-delta starter
(4) 3-point starter
Answer-1
Explanation-An Auto transformer Starter is suitable for a 20 kW squirrel cage induction motor.
Question-7.Compensating winding is used to
(1) Improve commutation
(2) Reduce armature reaction
(3) Reduce stray losses
(4) Improve look of machine.
Answer-2
Explanation-In order to neutralize the cross magnetizing effect of armature reaction, a compensating winding is used.
Question-8. _________ is cause of failure to build up voltage.
(1) No residual magnetism
(2) Actual field connections
(3) Less resistance
(4) High field current
Answer- 1
Explanation-Cause of failure to build up voltage in generator
- No residual magnetism of field
- Open field connection
- Field connection reversed
- Field circuit resistance too high
Question-9. __________ is done to improve efficiency and reliability of dc generator.
(1) Series operation
(2) Parallel operation
(3) Compound operation
(4) Load forecasting
Answer- 1
Explanation-Parallel operation is done to improve efficiency and reliability of dc generator.
Question-10.V curve is a graph of
(1) Armature voltage, Field current
(2) Field voltage, Field current
(3) Armature current, Field current
(4) Field voltage, Armature current
Answer-3
Explanation-V curve is a graph of Armature current and Field current.
Question-11.Thyristor is a __________ Layer and __________ Terminal semi-conductor device.
(1) 3, 3
(2) 3, 2
(3) 2, 2
(4) 4, 3
Answer- 4
Explanation-A thyristor is a solid-state semiconductor device with four layers of alternating P- and N-type materials.It have three terminal-Anode,Cathode,Gate
Question-12.Which among the below stated Boolean expressions do not obey De-Morgan’s theorem
(1) X’+Y’=X’.Y’
(2) X’.Y’=X’+Y’
(3) X.Y=(X+Y)’
(4) X’+Y=X.Y
Answer- 3
Explanation– According to De-Morgan’s theorem-The complement of the product of two or more variables is equal to the sum of the complements of the variables.
Question-14. Which of the following quantities are same in all parts of parallel circuit
(1) Resistance
(2) Voltage
(3) Power
(4) Current
Answer-2
Explanation-Voltage is the same across each component of the parallel circuit.
Question-14. Power factor is the ratio of
(1) Resistance to Inductance
(2) Inductance to Capacitance
(3) Resistance to Impedance
(4) Inductance to Impedance
Answer-3
Explanation-Power Factor=Cos(θ) = Real power (P)/Apparent power (S)= W/VA =R/Z
Question-15.The unit of resistivity is
(1) ohm-meter
(2) mho-meter
(3) ampere-meter
(4) voltage-meter
Answer-1
Explanation-Electrical resistivity is a fundamental property of a material that quantifies how strongly it resists the flow of electric current. A low resistivity indicates a material that readily allows the flow of electric current.The SI unit of electrical resistivity is the ohm⋅metre (Ω⋅m)
Question-16. The Load factor
(1) is always more than 1
(2) is always less than 1
(3) 1
(4) 0
Answer- 2
Explanation-The load factor is defined as the average load divided by the peak load in a specified time period,It is always less than 1
Question-17.. Nuclear power plant is normally used for
(1) Base load
(2) Peak load
(3) Average load
(4) Any load
Answer- 1
Explanation– The base load power plants typically are nuclear plants or coal-fueled,due to low-cost fuel and steady state power they can produce.
Question-18. From below which power station has maximum efficiency
(1) Steam Power Station
(2) Hydro-electrical Power Station
(3) Diesel Power Station
(4) Nuclear Power Station
Answer- 2
Explanation–
Hydro Power station-85% efficient
Nuclear Power station-55% efficient
Diesel Power station-35% efficient
Steam Power station-25% efficient
Question-19.Which of the below metal is not used in Nuclear power plant as fuel
(1) Uranium
(2) Thorium
(3) Plutonium
(4) Magnesium
Answer- 4
Explanation-Metal is used in Nuclear power plant as fuel is enriched uranium (U-235) or reprocessed plutonium (Pu-239) and thorium.
Question-20.Which of the following power plant has practically no stand by loss
(1) Hydro-electric power plant
(2) Diesel power plant
(3) Nuclear power plant
(4) Steam power plant
Answer- 1
Explanation-Hydro Power station-85% efficient-This Plant has no stand-by losses
Question-21.What is the value of Load Factor
(1) <1
(2) >1
(3) >=1
(4) <0
Answer- 1
Explanation-The load factor is defined as the average load divided by the peak load in a specified time period,It is always less than 1
Question-22. In electric welding, arc blow can be avoided by
(1) using ac machines.
(2) increasing arc length.
(3) using bare electrodes.
(4) welding away from ground connection.
Answer- 1
Explanation-Arc blow is the undesirable effect of a electric welding during arc welding. They are two kinds of arc blow-Magnetic and Thermal.In electric welding, arc blow can be avoided by using ac machines.
Question-23.Which switch use in Staircase Wiring Circuits
(1) One way switch
(2) Two way center off switch
(3) Two way switch
(4) Double pole main switch
Answer-3
Explanation-Two way switching means having two or more switches in different locations to control one lamp. It use in Staircase Wiring Circuits
Question-24.Minimum size of the aluminium conductor in domestic wiring is
(1) 1.0 sq.mm.
(2) 2.5 sq.mm.
(3) 0.5 sq.mm.
(4) 1.5 sq.mm.
Answer-3
Explanation-Minimum size of the aluminium conductor in domestic wiring is 0.5 sq.mm.
Question-25.The material most commonly used for overhead line insulators is
(1) Rubber
(2) Wood
(3) Copper
(4) Porcelain
Answer-4
Explanation-Porcelain in most commonly used material for over head insulator.