# Technical Questions for ALP & Tech. Part-6

## Technical Questions for ALP & Tech. Part-6

This Test is very much helpful for Assistant Loco Pilot and Technician written Exams. This Test is based on Previous Loco Pilot Exams. #### Useful for all Railway Technical Exams

1. A dc series motor should not be started:

2. The air gap between stator and armature of electric motor
(a) To get a stronger magnetic field
(b) To improve the air circulation
(c) To reach a higher speed of rotation
(d) To make the rotation easier

3. A polyethylene piece rubbed with wool is found to have a negative charge of 3.2×17-7 coulomb. Estimate the number of electrons of electrons transferred.
(a) 2×1011
(b) 2×1012
(c) 3×1011

(d) 3×1012

4. Coulomb’s law is given by F=KQ1Q2rn where n is:
(a) ½
(b) -2
(c) 2
(d) -1/2

5. If a positive charge is shifted from a low potential region to high potential region, the electric potential energy:
(a) Decreases
(b) Increases
(c) Remains the same
(d) May increase /decrease

6. When a dielectric slab is introduced between the plates of a capacitor connected to a battery.
(a) Charge on capacitor increases
(b) Potential difference across the capacitor increases
(c) Capacity remains same
(d) None of these

7. The commercial unit of electric energy is a kilowatt-hour (kwh). 1 kwh is equal to?

(a) 3.6×103 J
(b) 3.6×106J
(c) 3.4×103  J
(d) 3.5×106  J

8. The specific resistance of copper, silver and constantant are 1.78×10-6 ohm-cm,10-6 ohm cm, and 48×10-6 ohm-cm respectively. Which is the best conductor?
(a) Copper
(b) Silver
(c) Constantan
(d) Copper and Silver

9. A piece of copper and another of germanium are cooled from room temperature to 40 degrees K, the resistance of?
(a) Each of them decreases
(b) Each of them increases
(c) Copper increases, germanium decreases
(d) Copper decreases, germanium increases

10. How much current is drawn by a motor of 0.5 HP from 220 volt supply?
(a) 1.2A
(b) 1.4A
(c) 1.7A
(d) None of these

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1. Q.10 Explanation:

1 HP= 746 Watt

Power, P=VI
0.5×746=220xI
I= 1.7 A (Ans)

2. Q.8 Explanation:

Good conductor is one which has low resistance. So, in this question we have to find conductor with lowest resistance.

We know that, R=ρL/A
where ρ is specific resistance of conductor.
For fixed length and cross-sectional area. R∝ρ
Means the conductor which has lowest specific resistance (ρ) has lowest Resistance and so good conductor.
So, Silver is best conductor out of all given option. Ans-b

3. 8th ques explain plz

4. I want explanation for ques no 8

5. Already explained in above comment.

6. Q.6.
Explanation:

Dielectric= An insulating material such as paper or plastic placed between the plates of a capacitor to maintain a physical separation of the plates is called dielectric.

When a dielectric material is inserted to completely fill the space between the plates, the capacitance C=KexC0
[Where C=Final Capacitance of the capacitor, Ke=dielectric constant, C0=Initial capacitance of the capacitor]
Value of Ke [Dielectric Constant] is always greater than 1
So, When a dielectric material is inserted between the plates of a capacitor, Capacitance increases.

And we know that, Q=CV [Here Voltage is fixed, so Q ∝ C ]

Q ∝ C, and here in this question C increases so, Q also increases. ie Charge on Cpacitor increases. [Ans]