Electronics Interview Preparation Guide
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Electronics Interview Questions and Answers will guide now that Electronics is a branch of science and technology that deals with the flow of electrons through nonmetallic conductors, mainly semiconductors such as silicon, basic example is computer and mobile. It is distinct from electrical science and technology, which deal with the flow of electrons and other charge carriers through metal conductors such as copper. Learn more by Electronics Interview Questions and Answers Guide.

26 Electronics Questions and Answers:

1 :: 6dB pad introduces how much attenuation?

If you are talking about power, a 3db gain cuts the signal in half and another 3db gain, for a total of 6 cuts the signal in half again for a total attenuation of 75%.

2 :: How to check the Mobile Battery charge status?

You can tell the state of charge on a 9V battery by touching both poles across your tongue. If it tingles, the battery still has life. If not, throw it away.

3 :: What is the exactly meaning of manual testing?

Exact meaning of Manual testing is,testing the software or any application by manually without use of automation tools.

5 :: Explain negative test cases for testing
mobile phones?

Negative test cases for testing mobile phones:

1.removing the SIM card and made a call
2.by invalid phone number
3.made a call at which there is no tower signal
4.Made a call after removing the battery or at no power in battery and also we can add some more points...

6 :: What is the difference between TDMA and FDMA?

Time division multiple access (TDMA) is a channel access method for shared medium (usually radio) networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using his own time slot. This allows multiple stations to
share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity. TDMA is used in the digital 2G cellular systems such as Global System for Mobile Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, and in the Digital Enhanced Cordless Telecommunications (DECT)
standard for portable phones. It is also used extensively in satellite systems, and combat-net radio systems.

Frequency Division Multiple Access or FDMA is a channel access method used in multiple-access protocols as a channelization protocol. FDMA gives users an individual allocation of one or several frequency bands, allowing them to utilize the allocated radio spectrum without interfering
with each other. Multiple Access systems coordinate access between multiple users. The users may also share access via different methods such TDMA, CDMA, or SDMA. These protocols
are utilized differently, at different levels of the theoretical OSI model.

7 :: What will be the common test case for SMS and Mp3 player applications?

There might be many common test cases: Here are 2
1. For SMS: It uses UDP protocol
2. for MP3: Audio streaming also uses UDP protocol

1. for SMS: For entering text for SMS, you need to open Text editor.
2. for MP3: For entering/editing play list names, text editor should be opened.
So, the test cases written for text editor can be used for both applications.

8 :: How many memory locations can be addressed by a microprocessor with 14 address lines?

no of memory locations that can be addressed is 2 to the power of no. of address lines i.e. 2 power 14

9 :: Which type of architecture 8085 has?

CISC Architecture

10 :: How do you make a memory card of mobile phone?

A memory chip stores bits and mounted in a card with electrical contacts so a computer or camera can send data to be stored. There is not much more to it than that.

11 :: Why do I not see the battery and capacitor combination for power backup?

There are "super capacitors" that are used for power backup - they are efficient for short-term power take-over, but they are leaky and are not good for long term. Batteries tend to die slowly, more slowly than the leakage on a power backup capacitor, so the capacitor does not do any good. Regular capacitors store so little energy they cannot really be a power source.

12 :: When recording infrasound waves or microwaves how do they differ from one another? What is the best way to read them?

By microwaves, do you mean radio signals, like in a microwave oven? These have nothing to do with sound. There is no way to "record" microwaves really.

Sure, you can build a microwave transmitter with lots of power, enough to cook everyone in a building if you wanted to. The military has a microwave gun that heats up your skin painfully at a good distance (of course, all you do is wear aluminum foil and it does not affect you at all).

13 :: How can we prove that radio waves are sine waves? What makes them sine?

Fourier says that only a sine wave has no harmonic content. The math works out that if you have any wave shape other than a sign wave, you can break it down into a group of sine waves of different harmonic frequency, phase, and amplitude. All those harmonics go to zero when the wave shape is a pure sine. We can tell that radio waves behave like a sine, you can run them through a narrowband filter, and no energy is lost. Maxwell's equations predict propagation and fields based on a sine wave, and anything other than that propagates as if it is multiple frequencies, which do not propagate energy as well. So mathematically, radio waves work as they measure to work only if you assume they are sine waves.

14 :: Is it possible to reverse the order of a Variable Frequency Drive? Ex: I want to be able to create 120v power from a variable speed engine, with at least 6kw of power.

You say many alternators, but really, you need only one. The more I think about this, the more I think it is not so hard to do. If you have a 6KW alternator, it's possible that it has some kind of voltage regulation, maybe the rotor is not a permanent magnet, but an electromagnet with ring brushes, and there's a regulator circuit that drives this to keep the voltage constant regardless of frequency. If this is the case, what I would do (not many would try this) is rectify this to make 150 volts DC with a simple rectifier bridge and filter cap (total maybe $30). Then buy some 1KW inverters, and tap into them after the DC-DC converter (the part where it takes in 12VDC and steps it up to 150 VDC), drive the 150VDC in at that point, then let it switch this to AC for you. You could put 6 of these all running from the same alternator, so you could run 6 1KW loads.

Now taking this idea a step further, I would realize that the DC-DC converter is most of what you are paying for in the inverter, and it is the source of inefficiency in the inverter. So you are wasting a lot of money and watts, and so I would copy the circuit out of it that does the switching (4 power FETs and a 60 cycle driver) and have my inverter done much cheaper.

15 :: Why does charging batteries take lengthy periods? What can be done to quicken the speed?

Batteries work through a chemical process, some kind of ion exchange where the battery contains two elements that want to combine ions and give up an electron to cause current flow. They do this energy release all by themselves with no energy added, it wants this exchange to happen it is more stable after the reaction. Therefore, to charge the battery you are forcing things to go backwards, which the reaction does not like. By adding a current, you are making the reaction reverse. This is not an efficient process, and usually takes more energy than is given back, like more than twice as much takes (depends on the battery type). Where does the extra energy go? It is into heat mostly.

Therefore, the problem with fast charging is you cannot put so much energy back that you get the battery too hot and melt it down. You can charge a battery at a much higher rate than you discharge it, so you can make the charge cycle take less time than the discharge (this depends on the discharge rate as well, of course). However, you are limited by the heat, so a 1-minute charge of your electric car just is not possible.

16 :: What do mean by "flow of electron"?

Flow of electrons is just what it says - electrons flow down a wire that is what current, is. Good conductors like copper and silver and aluminum have free electrons in their outer shells, and they jump from atom to atom down a wire. It is somewhat similar to water flowing down a pipe.

It's kind of amazing that you can force this to happen with a battery or a magnet, and that you can transfer energy this way, but that's what it does.

17 :: What are encoder and the decoder? What are the uses of these two devices? Also, write about how it works with circuit diagram.

There are zillions of things in electronics called encoders. You can look up LCDs and NAND gates as well and this is really basics.

18 :: Do you have any ideas how to make a ping-pong ball launcher that reloads automatic and shoots automatically?

Air cannon is probably the simplest, PVC pipe from Home Depot and shoots things very far, can make any size you want, need a tire pump or air compressor to power it. It is also called Potato Cannons for obvious reasons. I shot a potato over 1000 feet with 60 psi and 2" pipe.

19 :: Is it possible to build an AC or DC variable-speed generator with a variable field current, controlled by a signal from a torque sensor connected to the shaft of the generator (i.e., net torque = 0)?

You can control the field with anything, but why would you do it with torque? Why do you say net torque=0? What is the significance of variable speed?

I am trying to think of why you would do this. If the torque were low, you could increase the field to generate more energy, which would make the torque go up. That is positive feedback, but maybe it is constant power into a resistive load (voltage would go up). If you did negative feedback, that would mean the field would reduce as the torque went up, reducing the torque, so you would have a torque regulator. This would probably be good for a wind generator, as you want to control the torque to match the wind speed to get maximum energy out, but this would also vary the output of the generator a lot. Maybe if you were heating water this would work.

20 :: What is the significance of "4-20 mA" signal in hart protocol?

The HART protocol is an old Frequency Shift Keying way of sending data, typically from highway sensors. This is a very old standard by today's standards there are so much better ways to send data. Of course, 4-20 ma loops are even older, dating back over 50 years, and still in common use. Must be something good about it - it is simple.

4-20 ma loops are a way to send an analog value, like temperature or position, over a pair of wires. It is simple on the surface, 4 mA is the minimum, and 20 mA is the maximum of the range. The cool thing about this is that it is constant current, not a voltage, so line resistance does not matter. Anything, constant current looks like an open circuit, so it is supposedly immune to noise (though in reality it still has noise pickup problems). However, why not 0 to 20 mA the cool thing is you can power the remote sensor. You are running a current through the remote you have a voltage at the driving end why not use some of that power to run the electronics in the sensor? Therefore, if the sensor pulls less than 4 ma and you make the range 4-20, you always have enough current to power the remote at the same time.