# I want to understand everything about transistor and capacitor

Discussion in 'General Electronics Discussion' started by Youngfella, Feb 1, 2013.

1. ### Youngfella

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Feb 1, 2013
A
capacitor:-
Sometime ago i wanted to know everything about a capacitor and a diode,4rm what i learnt capacitor can store voltage and can act as a block(block dc & allows ac)
1-ok first question how does a capacitor stores electricity is it that u must connect anode and cathode(question is it connected in series with the power source) to d capacitor and if it stores it when does it release it
2-a capacitor can block dc and allows ac how? But theoritically there is an insulator btw a capacitor and i heard capacitors can block dc and pass ac when conected in parallel(ie connected to only one terminal) ok how does the voltage pass through d insulator
B
transistor:-
i learnt transistor act as diode and can amplify signal(i dont understand is it that it amplifies and turn electricity to ac)
i learnt it also has terminals am going to deal with npn only,ok n-p-n means negative positive negative(right) since p is d base then is it that i must connect positive to base and negative to collector and it will emmit negative 4rm emmiter,ok how can negative and positive meet together its like impossible,so it tried d same connection and d transistor started burning,then i thought how can negative and positive meet so i changed it and i put positive to base(to open d transistor)and i connected positive to collector which is suppose to be n(negative) and i assumed the emitter will realese positive so i connected it to a led and it lighted up,i just dont understand i practiced the reverse of what ive learnt and it worked,and i was 100% sure it was an npn transistor...pls help and share any knowledge u know abt transistor and capacitor based on hw they ar connected and used.thanks

Last edited: Feb 1, 2013
2. ### BobK

7,682
1,689
Jan 5, 2010
You need to start with a basic electronics textbook and read and understand it. "The Art of Electronics" by Horowitz and Hill is a good one.

Bob

3. ### john monks

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Mar 9, 2012
Current does not pass through a capacitor. A capacitor is two plates separated by an insulator. They work by electrostatic forces. When you connected a battery across a capacitor the negative terminal of the battery passes current into the plate connected to it. This causes electrons to pile up on the plate creating a negative electrostatic field. This field passes through the insulator and pushes an equivalent numberer of electrons off the opposite place and into the connecting wire back to the positive terminal of the battery. The number of electrons that pass to and from the plates is directly proportional to the strength of the field or that is the voltage. Once the voltage is reached across the insulator and no longer changes, no electrons are passing to or from either plate. Electrons start flowing when the voltage or the field strength changes across the capacitor.
So it appears that alternating current passes through a capacitor but not direct current. But in reality no current is passing through the capacitor. Current is merely piling up or being depleted from the plates inside the capacitor.

I don't follow what you are doing with the transistor so I can't help there. But I would suggest using a series resistor and a battery when experimenting with transistors. You may have damaged your transistor.

On a PN junction current flows when a negative lead is placed on the N lead or the cathode and the positive placed on the other. It acts like a check valve permitting current to pass in one direction and not the other.

Transistors a trickier but I would suggest getting some transistors, resistors, and a battery and trying again.

4. ### sjgallagher2

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Jan 27, 2013
If you need such information, look at Forrest M. Mims book Getting Started in Electronics. It's not \$100 like the art of electronics, and it's available at most Radio Shack stores! it covers a ton of stuff, with nice drawings, it was my first book and it was exactly what I needed since I didn't understand what I needed to about capacitors and transistors, as well as tons of other things. It's really a complete introduction, and it's so simple, you realllly should get it