Saturday, November 3, 2012

TCS Campus Interview Questions Answers

These questions were asked in TCS campus interview at Govt. College of Engineering, Tirunelveli.

1. Tell me about yourself
2. About TCS
3. As a electrical engineer, why software company

4. Draw AND gate












5. what is difference between latch and flipflop

A flip-flop continuously checks its inputs and correspondingly changes its output only at times determined by clocking signal.
A latch is a device which continuously checks all its input and correspondingly changes its output, independent of the determined by clocking signal.


6. Types of flipflop:
There are basically four main types of  flip-flops: SR, D, JK, and T.


7. Do you know C
8. Are you willing to travel for onsite

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Thanks for reading. Please leave your comments below.  Please share your interview experiences. We will post it with answers which will be useful for our readers.

Goodrich Interview: Exp.-2010

These questions are asked in the technical interview conducted in Goodrich, Bangalore for the post of Design Engineer with 2 year experience. As it is for the experienced engineers, we would have to explain as much as possible about the topic. We did not answer the non technical questions here.

A1: Question about previous exp.
A2: Question about currently working project.
[1] Explain the amplifier operation of OP-AMP?
The golden rules of OP-AMP are:
1. Vout = A. Delta Vin  [ A = Gain, Delta Vin = V+  -  V-]
2. V--  < Vout  < V++
3. Zout = 0    ,      Zin+ = Zin- = Infinity

The opamp will work as inverting amplifier and non- inverting amplifier based on the supply applied to its terminals.

Non Inverting Amplifier:
V_{\text{out}} = V_{\text{in}} \left( 1 + \frac{R_2}{R_1} \right)\,


Inverting Amplifier:

V_{\text{out}} = -\frac{R_{\text{f}}}{R_{\text{in}}} V_{\text{in}}\!\,


[2]Interrupted and Asked to derive the equation...
Current i =  (Vin-Vout) / (Rin+Rf)

              =( Vin - Vx)/Rin = (Vout - Vx)/Rf

Vx = virtual ground =the node at inverting input terminal =0

[3] Interrupted and asked what is virtual ground?
Explained.
then  i = Vin/Rin - Vx/Rin = Vout/Rf- Vout/Rf

Rearranging we will get the final equation.

[4] Explain how transistor acts as a switch?
The areas of operation for a transistor switch are known as the Saturation Region and the Cut-off Region
This means then that we can ignore the operating Q-point biasing and voltage divider circuitry required for amplification, and use the transistor as a switch by driving it back and forth between its "fully-OFF" (cut-off) and "fully-ON" (saturation) regions as shown below.


Transistor Switch Operating Regions


A3: Why do you want such a high salary which is well above the market average?

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Thanks for reading. Please leave your comments below.  Please share your interview experiences. We will post it with answers which will be useful for our readers.
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Off Campus Interview for a Fresher

These questions are given by one of our reader. He shared his experience. Please share yours...It is more informative if you mention the company name etc....
What is the Scope of Electrical Engineering?
[ This question is mostly asked to check your communication. Speak  casually. Tell the importance of electrical and electronics engineering course, what are the topics to be covered in the course, what are the job prospects etc.]

Answer: Electrical Engineering has a very broad scope with the science and technology which involves electricity, electronics, and electromagnetism in order to design, construct, and maintain products, services, and information systems.
Electrical Engineering is a branch that deals with the field associated with power transmission and motor control.
Electrical engineering  is one of the core fields of engineering, so it is always evergreen in terms of job prospects.
Electrical Engineering is the heart of whole engineering discipline.
Nowadays, we see  Electronics playing an important role in the implementation and control of Electrical Machines. Keeping this fact file in mind the course have transformed from core electrical Engineering into a Fusion of Electronics and Electrical and has been renamed as Electronics and Electrical engineering.
Electricity has become the basic need for survival, globally. From household to industrial plants, communication and satellite navigation system, electronic equipment, computers etc., all require electricity.
Electrical engineering thus deals with study and application of electrical systems for use in these different environments. It equips you with the knowledge of transmission and generation of electrical power, electrical circuit design, electronics, instrumentation, control system, understanding electrical and electronic networks etc.
The course also covers the study of electronic devices and circuits involved in measurement, instrumentation, control and protection of electrical equipments and conversion systems. Concept of computer and recent applications of computer based systems in design, analysis and efficient operation of power system, maintaining quality and security, also included in the course.

What does '230V AC Supply' really mean? Is it the RMS or peak voltage?
If the peak value is meant it should be clearly stated, otherwise assume it is the RMS value. The supply is 230V AC means 230V RMS, so the peak voltage of the mains is about 320V. 

What does the multimeter in volt meter mode show? Is it the RMS or peak voltage?
If the multimeter is in voltmeter mode and when it connects to AC circuits it shows the RMS value of the voltage or current. When it connects to varying DC signals it will show RMS value only.

How does Induction Motor work?
Induction motors are also known as rotating transformer.( Primary winding is stator and secondary winding is rotor).
When the 3 phase stator windings are fed by 3 phase supply a magnetic flux of constant magnitude, rotating at synchronous speed is generated. These flux passes through the air gap, sweeps past the rotor surface, cuts stationary rotor conductors.
According to Faraday's laws of electro-magnetic induction, an emf is induced in the rotor. This emf frequency is same as supply frequency.
As rotor conductors form a closed circuit, the induced emf produces a current. It's direction will oppose the cause producing it ( according to lenz's law). 
In this case, the cause is relative velocity between the rotating flux of the stator and stationary rotor conductors. So to reduce the relative speed, the rotor starts to run in the same direction of the stator flux.
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Power Electronics Graduate Trainee Interview [BGR Energy]

These questions were asked in Power Electronics Graduate Trainee Interview conducted by BGR Energy Systems Company at MIT Chennai.

[1] Draw and Explain the SCR V-I characteristic?
Vak = +ve & Vg = 0
(i) When a positive voltage is applied to anode with respect to cathode, the junctions J1 and J3 are         forward biased, but the junction J2 is reverse biased. 

(ii) The SCR is in its forward blocking state. At this time the Gate signal is not applied. 

(iii) As shown in figure a small amount of forward leakage current is flows through the device.

Vak = + & Vg = +ve
(i) When the small amount of positive voltage is applied, while positive voltage is applied to anode with respect to cathode, the junction J3 becomes forward biased. 

(ii) Thus the SCR conducts a large value of forward current with small voltage drop. With the application of gate signal the SCR changed from forward blocking state to forward conducting state. It is called as latching.Without gate signal it happens at forward breakdown voltage (Vfbd).

(iii) When the gate signal value is increased, the latching happens for low Vak voltages as mentioned in the figure. In the presence of forward current (i.e. after the thyristor is turned on by a suitable gate voltage) it will not turn off even after the gate voltage has been removed.  

(iv) The thyristor will only turn off when the forward current drops below holding current. The holding current is defined as the minimum current required to hold the SCR in the forward conduction state.

Vak = -ve
(i) When a negative voltage is applied to anode with respect to cathode, the junctions J1 and J3 are reversed biased, but the junction J2 is forward biased. The SCR is in its reverse blocking state. 

(ii) As shown in figure a small amount of reverse leakage current flows through the device. 
If the applied voltage is more than reverse breakdown voltage, the device will collapse and the large amount of current flows through it.

[2] Explain Buck topology
(i) When the switch is ON condition (ie, TON), the input provides energy to inductor and output. 
(ii) The difference between the input and output voltage is applied to inductor as shown in the below waveform.
(iii) When the switch is turned off, the inductor current will flow in the same direction to load. It is inductor property to maintain the current flow in the same direction.
(iv) The freewheeling diode D1 is forward biased at this time and completes the inductor current path.

The output of the buck converter with continuous output current is 

Vout = D*VIN

D = Duty cycle = TON / [TON + TOFF]

[3] Compare MOSFET and BJT
             BJT                                                                     MOSFET
More Power handling Capability                             Less Power handling capability
Low switching speed                                             Fast switching speed
High On state resistance                                        Low on state resistance
Has second breakdown voltage problem                 No second breakdown voltage problem