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Electrical/ Electronics and communication engineering core interview questions.

hi puys, panel in mba interviews always grill on acads related questions. so plz help out each other n post core questions that can be asked in management college interviews
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How can a 40w tube lite be started with 230v AC/DC without using any choke/Coil?

Where are VCBs, OCBs, ACBs used and why ?

like ACBs are used in panel main incomers, VCBs at transformer outgoings etc....

  • VCB is used in HT and ACB is used in LT. Reason: Dielectr.... 15 Mar '14.
  • @Nitesh27 plz help. 15 Mar '14.
Nitesh Bhuwania @Nitesh27 122
VCB is used in HT and ACB is used in LT. Reason: Dielectric strength of vacuum is more than that of air. HT voltage is more than LT. So, VCB is used in HT and ACB in LT. OCB are used in the voltage range of 11kV and 132kV applications. They are installed in units, example for 66kV application 6 OCB are used.
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Ceiling fans rotate anticlockwise while table fans clockwise why?

tried searching on google..but din understand

  • @Nitesh27 thanx...but cant we use a table fan as ceiling .... 14 Mar '14.
  • This is mainly because of the diversity in their working .... 14 Mar '14.
Prateek Sinha @prateeksinha04 3,113
@Nitesh27 thanx...but cant we use a table fan as ceiling fan...i mean the motor ???
Nitesh Bhuwania @Nitesh27 122

This is mainly because of the diversity in their working principles. Every fan needs a motor that allowsrotational motion. Taking into consideration the structure of a motor, there are two major parts - The motor itself and the armature. Out of these two parts, one part is always stationary while the other moves around it's axis allowing rotation of any object that is attached to it. Ceiling fans have a stationary armature and the motor moves in the counter-clockwise direction. Since, the blades of the fan are attached to the motor, the ceiling fan rotates in an anti-clockwise direction. It is exactly opposite for a table fan. The motor is stationary and the armature moves to give motion to the fan blades. Because of Newton's 3rd law of motion that states - "Every action has an equal and opposite reaction.", the stationary motor gives the armature a push in the opposite direction. This causes the blades of the table fan that are attached to the armature, to move in clockwise direction

I said : i have done robotics .

IIM interviewer : wt r degrees of freedom..how many ,,wts pitch -roll?

photodiode and solarcell both are different

solarcell depends on the conversion of energy from one form to another ie it is converting light energy into electrical energy .... while a photodiode is already biased but current can't flow through it untill some source of light fall on it and drops the potential of the barrier junction so that the current can flow through it (these are generally used in reverse biased condition)....PIN and APD are best example of these type

How to speed up / slow down a series of rectangular pulses
a) analogous procedure
b) digital process?
Why are functions of basis function similar to each other?
IIM L calling. :) 

Can anyone post something on WiMax?

What is the difference between a Laptop and a Notepad. Explain in Electronic design.

maalik dil jeet lia...
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UDT 2012, BDT 2012,Cat 2012-99.78, Converts- IIM C,IIM L,FMS. Wl-XL. Rejects-IIM A. 

yeh dekho .. not sure how much it'll help
I am in no position to explain any acads to a panel .. only know basic phenomena behind these devices

1. Explain the working of a diode.
Diodes are devices that allow current to flow in one direction but oppose flow in the reverse direction. Could restate it as having low resistance in one direction/ high resistance in opposite. Most common forms of diodes are LEDs, Zener diodes, p-n junction diodes.

LEDs when biased have carriers re-combining. This results in them reaching lower/more stable energy states from their earlier states when they were separated. The energy released when reaching the more stable states is seen in the form of EM radiation of different frequencies .. this can be blue/red/UV/IR ..

p-n junction diodes contain two separate regions of semiconductor material doped differently to setup the p/n regions. They aren't joined together. The junction is where a depletion region is created by the re-combination of holes and electrons. This is what allows carriers to flow through easily in one direction and opposes the flow in the opposite.

Zener diode is an extension of this in that it will allow current to flow in the opposite direction at a reduced reverse biased voltage. This is where it is used to protect circuits. The phenomeon is Zener breakdown where a voltage difference over the small depletion region results in a large electric field which pulls out carriers in the opposite direction ( something similar to corona discharge, lightning .. might be an oversimplification .. ). Avalanche breakdown is also similar to this and both phenomenon occur at the same time. The difference between the two diodes is that ADs maintain a small voltage across them in breakdown but ZDs don't. Not very sure about this in more detail ..

Schottky diodes are also somewhat similar to p-ns but they have additional metal/silicon junction that gives faster switching times ... you could mention bias voltages of diodes .. silicon 0.7V, germanium 0.3V, SD 0.15V etc ..

2. Explain Zener diode, knee voltage, breakdown voltage. Applications.
Breakdown voltage is that voltage at which an insulator starts conducting. The limit in Zener diodes is Zener voltage .. avalanche point and all such terms are similar to this. Insulating material is ionized by application of strong voltage. Avalanche in diodes, Corona in fluids, Lightning/sparks in air ..

ZDs could be used to protect circuits from unexpected surges by placing them in reverse bias .. When a surge happens, it will breakdown because of its design easily, allow current to pass through it easily, protect the circuit. Current won't flow through the circuit because it will offer more resistance to current than your reverse biased ZD ..

3. Explain Impatt, Schottky, and Tunnel diode. Applications.
IMPATT, Tunnel used in high frequency electronics. iske aage jyada nahi pata ..
IMPATT uses the fact that an electron when accelerated to impact an atom can knock out an electron from it ... thus causing an avalanche effect

Tunnel diodes have a very thin p-n junction that allows quantum tunneling to kick in ..
iske jyada kahan kaise use hota hai .. pata nahi .. TBH never studied about them in any detail ..

5. What are Flip Flops?
Basic elements of memory .. bistable electronic device .. state can be controlled either by changing the level of input ( as in latches ) or my the edge of the input ( as in flip flops ) .. mostly basic wikipedia stuff ..

Rank 16 to 456 : 440 V jhatka :P  

Frequently asked questions to me in interviews:

1. Explain the working of a diode.
2. Explain Zener diode, knee voltage, breakdown voltage. Applications.
3. Explain Impatt, Schottky, and Tunnel diode. Applications.
4. Difference between BJT, JFET and MOSFET. Arrange them in order of applicability and explain why.
5. What are Flip Flops?

@retry , how would you answer these? Main toh thoda vague hu inme, and articulation main bhi fight hai thodi. Can you explain?
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"I am the master of my fate, I am the captain of my soul" - Invictus|| UDT '12, MMDT '12, '11. Quora: http://www.quora.com/Omkar-Parab-1
@sarvshwet The basics of engineering won't change. Thanks for sharing!

1.What do 0 and 1 in digital signify?
2.What are the different number system used in digital electronics?-IIM k

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