Hi,

I have become fond of electronics just few months ago. I know some little theory and other important mathematical expressions of different circuits and other small equipments.
But I just don't know or I want to know that how I know when or where I should use a capacitor or a transistor or something like that. Or what transistor or capacitor or resistor I should use. Say I want to make a circuit which will produce a chirping sound so how I know that what will be the circuit or what will be the measurement of all the stuffs.
Also please let me know how to check a transistor and capacitor using a multimeter.

Thanks and Regards
Circuiting.

So many questions, and I'm afraid you might not like all my answers.

Part 1:
A capacitor is a device that stores electric charge. Capacitance is a measure of the total charge per measure of electric potential. Thus:
C = Q/V

Consequently the current across a capacitor changes with time because as current flows through a capacitor, charge builds up and the voltage across it rises. To spare you the details, as it happens, the current is the derivative of the charge with respect to time:
dQ/dt

Now if all of this has you confused, here's a fundamental explanation. Think of conductors as pipes and electrons as water. Current is flowing water, and voltage is water pressure. Now consider a wide pipe with a thin rubber membrane stretched across it. This represents a capacitor. If you flow water into the membrane, it will stretch until the force it exerts back equals the force of the water pressure.

You can use capacitors for things like oscillators and signal filters. For now though, it is mostly important for you to understand how current in a capacitor changes.

It would be much easier at this point for me to point you to a book called Getting Started In Electronics by Forest Mims. It's a little outdated, but the basics never change, and it is extremely well written for anyone who has not had formal education in electronics.

If I may ask, how old are you? And have you considered an education in electronics?

Hi DrLang,

Thank you very much indeed for your suggestions. I am 28 yrs old. I am an engineer
In Computer Science. But as you might know that CS does not include all the in-depth
Knowledge of electronics so I am not very good at that. As part of my curriculum we have
Studied only basic of electronics like how capacitor works or what the transistor is.
But I don't know what I am supposed to do if I want to design a circuit according to my needs. And you mentioned a book. Will it be available in india as I live in India. If not then how I will get it. Again thanks a lot for your suggestions..

Thanks and Regards
Circuiting

Learning how to design a circuit to do something that you want it to do is one of the ultimate products of an education in Electrical Engineering. For your situation, my suggestion would be to study the basics and look up projects that others have come up with. If you can figure out why the circuits work, you can sometimes modify them to your needs.

Being a Computer Scientist, you might also be interested to pursue digital electronics and embedded systems. You can program a microcontroller to do just about anything.

I don't know if Forest Mims will be readily available in India. However, if you can import, you can get it from Amazon.com (http://www.amazon.com/Getting-Started-Electronics-Forrest-Mims/dp/0945053282/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1218104924&sr=8-1).

Hi DrLang,

Thanks for your valuable reply. I am trying to get that book here at my home town. And also I am looking for some other sites for basic concepts in electronics. But I want to know another thing I asked in my first question and that is how I will check a capacitor or transistor using a multimeter.

Thanks and Regards
Circuiting

Most multimeters cannot check capacitors. Capacitors are hard to break, so there's usually no need to test them. Some multimeters are able to test the gain of a transistor, but this is usually not necessary because spec sheets that will list this are almost always readily available.

Zxc