# What Is A Current Source?

Discussion in 'General Electronics Chat' started by KASHOKAN, Mar 25, 2008.

1. ### KASHOKAN Thread Starter New Member

Mar 23, 2008
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Hi,
what is a current source ?

As for as voltage source is concerned, it is a potential energy generated by Alternator,Battery etc.. and according to ohms Law I = V/R i.e if voltage increases current also increases.

I want to know, what is the principle involved in current sources, because i have seen in industry for testing the circuit breakers they use current sources to test for rated current carrying capacity,overload testing by injecting current.

i ,was told that the voltage in a current source is less and it is constant, then how come it can inject such a high capacity current.

K.Ashokan

2. ### gotumal Active Member

Mar 24, 2008
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Current sourse is nothing but sourses a constant curent irrespective of load (ofcourse there is a range) unlike a volateg sourse which sourses a constant voltage over a range of load resisatnces.
To test parameters associated with current can be tested with current sourses.
Aother example I can give is; to measure temperature with RTD. Since you have a constant current in RTD. A voltage accross it will be a proportional to the temperature.

3. ### hgmjr Moderator

Jan 28, 2005
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Here is one section of the AAC ebook that talks about current sources.

If you read this section it will help put into context other replies to your question.

hgmjr

4. ### chrischristian Active Member

Feb 22, 2008
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Hmm.., I don't know that you like this or not but then even let me try to explain this in a simpler manner by water analogy,
Say, you have a water tank which is punctured at a point, now if you put a finger or better say a pressure meter at the point the meter will show you how much water pressure is there in the water tank, it will definately very high as the hole is very small and as the area of the hole is small then definately there will be much preasure, now you can consider the water preasure as the voltage ( the preasure of the charge stored in the battery), the water that will be leaking through the hole is the amount of current which is very small as the hole is very small and the hole it's self is the resistance (the size of the hole decides the resistance caused to the flow of water) which is small. So, here we have a voltage source which always have a small input resistance (small hole) , small amount of current (flow of water) and high voltage preasure (preasure of water),
Now comming to the current source, it has very inverse situation , think that the hole is too much big so there will be large flow of water and the preasure will be too low as the area of the hole would be too big (with the increase of area preasure decreases),So, here we have a current source with high input resistance( big hole), high flow of current (water flow )and very low voltage preasure (water preasure).That is it, at least I have learend it this way!!, Hope will help.

Apr 2, 2007
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