# circuit elements

Discussion in 'General Electronics Chat' started by kamarul amin, Jan 14, 2015.

1. ### kamarul amin Thread Starter Member

Dec 2, 2014
62
3
guys,, how can we know the differences between the ideal dependant sources and ideal independant source???

2. ### #12 Expert

Nov 30, 2010
16,655
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I'm a bit blurry about this, too. How can an ideal source be dependent? Great sex but no money?

3. ### kamarul amin Thread Starter Member

Dec 2, 2014
62
3
hmmm i dont know just learnt this topic about couple days ago but still cant understand it well. this is my first semester undergraduate

4. ### #12 Expert

Nov 30, 2010
16,655
7,293
OK! Good start. Now we know you have some education. If you tell us some more about where these sources come from and what they are about, we can probably get you some serious help.

5. ### kamarul amin Thread Starter Member

Dec 2, 2014
62
3
hm i'm not really sure about this source but it is the branches for active element. active element is the element that can generate energy. that is what i know so far. hehe

6. ### studiot AAC Fanatic!

Nov 9, 2007
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515
Well there is no mystery here.

Circuits are considered to be assembled from ideal elements for the purpose of analysis.
So the word ideal is really almost redundant.
It just means that, unlike real sources there are no loads that could cause it to fail.

So your question comes down to what is the difference between a dependent source and an independent one?

Well an independent source provides its voltage or current (Direct or Alternating) regardless of the conditions in the rest of the circuit.
A 9volt PP3 battery is a 9volt independent Direct voltage source, for the purposes of most circuit analysis.

A dependent source is a source whose value of current or voltage depends upon the voltage or current somewhere else in the circuit.
So dependent voltage source may supply a voltage equal to say 5 times the voltage at some other point in the circuit.
A dependent current source may supply a (constant) current equal to 3 times the current in some other branch of the circuit.

Last edited: Jan 14, 2015
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7. ### MikeML AAC Fanatic!

Oct 2, 2009
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V1 is an ideal (independent) voltage source which happens to be 2Vpp 10Hz Sine wave offset by +1V that creates V(x). It is independent because we get to specify what it is.

E1 is is an ideal dependent voltage source which producesV(y) which is -3*V(x). It is dependent on the voltage at node x.

Get it?

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8. ### ErnieM AAC Fanatic!

Apr 24, 2011
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First off, when you use the term "ideal" you are into the realm of fantasy as you cannot build an "ideal" anything.

Now fantasy may be a useful thing especially when it is a mathematical construct. An ideal source simply means a mathematical model where there are no parasitic parts, such as a voltage source that can put out an infinite current and still maintain the same voltage across itself.

An "ideal independent source" is simply something that supplies (sources) voltage or current and it does not depend on any other parameters. One example is a fixed voltage source, or a fixed current source.

An "ideal dependant source" does depend on some other parameter, such as current source that supplies a current of some multiple of anther current. One popular model of a transistor places a dependent current source between the collector and emitter, where the current is (beta) times the base current.

You know the difference by how the source is written. I would need to see what you are looking at to comment further.

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9. ### kamarul amin Thread Starter Member

Dec 2, 2014
62
3

know i get understand it better than before. still having a little bit confuse on dependent source. thank you bro

10. ### kamarul amin Thread Starter Member

Dec 2, 2014
62
3
yeah you make me understand about them now. hehe. thank you bro
it is said that there are four type dependent source, right??

i use this book ---> fundamentals of electric circuit by Charles K. Alexander/ Mathhew N. O. sadiku (fifth edition)

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11. ### kamarul amin Thread Starter Member

Dec 2, 2014
62
3
the graph make me nervous lol. i'm dont learnt this graph yet i think, because the lecturer just taught about the dependent and independent source.

12. ### studiot AAC Fanatic!

Nov 9, 2007
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To tell an independent source froma dependent one;

An independent current source will be labelled something like 5amps or whatever on the circuit diagram.
An independent sources has a fixed value.

A dependent current source will not have a specified current it will be labelled something like 5i2 so that if i2 changes so does the dependent current so that is always 5 times i2.
A dependent source does not have a fixed value.

Last edited: Jan 14, 2015
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13. ### WBahn Moderator

Mar 31, 2012
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You have two possible outputs for a dependent source -- voltage or current.

You have two possible controlling inputs for a dependent source -- voltage or current.

You thus have four possible combinations for a dependent source:
Voltage-controlled voltage source (VCVS)
Current-controlled voltage source (CCVS)
Voltage-controlled current source (VCCS)
Current-controlled current source (CCCS)

These are the main types. You could also have models that have different control parameters, such as a light-controlled source or a temperature-controlled source.

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14. ### kamarul amin Thread Starter Member

Dec 2, 2014
62
3

great!! thats what i saw in the example, some of the values just like 7i,5i, so it is dependent source. now you make me understand it better. thank you bro

15. ### kamarul amin Thread Starter Member

Dec 2, 2014
62
3

great explanation. thank you for helping me