interview questions 1

Before going to other topics on diodes let us know few interview questions

1.Why we can’t store AC in Batteries instead of DC.or Can we store AC in batteries instead of DC?

We cannot store AC in batteries because AC changes their polarity up to 50 (When frequency = 50 Hz) or 60 (When frequency = 60 Hz) times in a second. Therefore the battery terminals keep changing Positive (+ve) becomes Negative (-Ve) and vice versa, but the battery cannot change their terminals with the same speed so that’s why we can’t store AC in Batteries.

 

in addition, when we connect a battery with AC Supply, then It will charge during positive half cycle and discharge during negative half cycle, because the Positive (+ve) half cycle cancel the negative (-Ve) half cycle, so the average voltage or current in a complete cycle is Zero. So there is no chance to store AC in the Batteries.

 

Good to know:  Average Voltage x Average Current ≠ Average Power. 

C

Fig: Why we can’t store AC in Batteries instead of DC?

2.Why Motor rated in kW instead of kVA

Why Motor rated in kW/Horsepower instead of kVA?

We know that Transformer rating may be expressed in kVA as well as Generator and Alternator rated in kVA Designer doesn’t know the actual consumer power factor while manufacturing transformers and generators i.e. the P.F (Power factor) of Transformer and Generator/Alternator depends on the nature of connected load such as resistive load, capacitive load, and inductive load as Motors, etc. But Motorhas fixed Power factor, i.e. motor has defined power factor and the rating has been mentioned in KW on Motor nameplate data table. That’s why we are rated Motor in kW or HP (kilowatts/ Horsepower) instead of kVA.

In addition, Motor is a device which converts Electrical power into Mechanical power. In this case, the load is not electrical, but mechanical (Motor’s Output) and we take into the account only active power which has to be converted into mechanical load. Moreover, the motor power factor does not depend on the load and it works on any P.F because of its design.

3.Why Battery rated in Ah (Ampere hour) and not in VA.

Why Battery rating in Ah (Ampere hour) and not in VA.

Battery stores charge in the form of chemical energy and then converts it into electrical energy to utilize for a specific time. The amount of available charge is the capacity of a cell or battery which may be expressed in Ah (Ampere-hour). Moreover, in a charged battery, the numbers of molecules are limited to create a flow of electron in electric circuits, so, there must be a limited number of electrons in a cell/battery which they motivate through a circuit tofully discharge. Now we have the option to rate the battery capacity in Number of flowing electrons for a specific time, but, it would be a headache, because there are a vast number of electrons in it.  So we have another option (1C (Coulomb) = 6.25 x 10¹⁸electrons, or 6,250,000,000,000,000,000 electrons.

In addition, 1A (Ampere) = 1 coulomb of electrons per second and,

1h = 3600 Seconds

Therefore;

1Ah = (1A) x (3600s) = (C/s) x (3600s) = 3600 C.

∴ A (1 Ampere) = 1 Coulomb per second = C/s

But,

Why make up a new unit for battery capacity rating when an old one unit is doing just fine? L

Of course! To make your lives as technicians and students more difficult.   

As they do for electricity units… i.e. 1 Unit of Electricity = 1kWh = 1 board of Trade Unit…

4.The Main Difference between Active and Passive Components

Active and Passive Commonest (Very Easy Explanation with Examples)

 

Active Components:
Those devices or components which required external source to their operation is called Active Components. 
For Example: Diode, Transistors, SCR etc…
Explanation and Example: As we know that Diode is an Active Components. So it is required an External Source to its operation. 
Because,  If we connect a Diode in a Circuit and then connect this circuit to the Supply voltage., then Diode will not conduct the current Until the supply voltage reach to 0.3(In case of Germanium) or 0.7V(In case of Silicon). I think you got it 

 

Passive Components:

Those devices or components which do not required external source to their operation is called Passive Components. 
For Example: Resistor, Capacitor, Inductor etc…

 

Explanation and Example: Passive Components do not require external source to their operation. 
Like a Diode, Resistor does not require 0.3 0r 0.7 V. I.e., when we connect a resistor to the supply voltage, it starts work automatically without using a specific voltage. If you understood the above statement about active Components, then you will easily get this example. 

5.Expand ECE.

Electronics & Communication Engineering.

6) What is Electronic?

The study and use of electrical devices that operate by controlling the flow of electrons or

other electrically charged particles.

7. What is communication?

Communication means transferring a signal from the transmitter which passes through a

medium then the output is obtained at the receiver. (or)communication says as transferring of

message from one place to another place called communication.

8.Different types of communications? Explain.

Analog and digital communication.

As a technology, analog is the process of taking an audio or video signal (the human voice)

and translating it into electronic pulses. Digital on the other hand is breaking the signal into a

binary format where the audio or video data is represented by a series of "1"s and "0"s.

Digital signals are immune to noise, quality of transmission and reception is good,

components used in digital communication can be produced with high precision and power

consumption is also very less when compared with analog signals.

9) What is engineering?

The application of science to the needs of humanity and a profession in which a knowledge of

the mathematical and natural sciences gained by study, experience, and practice is applied

with judgment to develop ways to use economically the materials and forces of nature for the

benefit of mankind.

10) Difference between electronic and electrical.

Electronics work on DC and with a voltage range of -48vDC to +48vDC. If the electronic

device is plugged into a standard wall outlet, there will be a transformer inside which will

convert the AC voltage you are supplying to the required DC voltage needed by the device.

Examples: Computer, radio, T.V, etc...

Electric devices use line voltage (120vAC, 240vAC, etc...). Electric devices can also be

designed to operate on DC sources, but will be at DC voltages above 48v. Examples: are

incandescent lights, heaters, fridge, stove, etc...

11) What is sampling?

The process of obtaining a set of samples from a continuous function of time x(t) is referred

to as sampling.

12) State sampling theorem.

It states that, while taking the samples of a continuous signal, it has to be taken care that the

sampling rate is equal to or greater than twice the cut off frequency and the minimum

sampling rate is known as the Nyquist rate.

13) What is cut-off frequency?

The frequency at which the response is -3dB with respect to the maximum response.

14) What is pass band?

Passband is the range of frequencies or wavelengths that can pass through a filter without

being attenuated.

15) What is stop band?

A stopband is a band of frequencies, between specified limits, in which a circuit, such as a

filter or telephone circuit, does not let signals through, or the attenuation is above the required

stopband attenuation level.

i will post interview question in between the topics