# explaining a rule from superposition Principle.

Thread Starter

#### SUN SHINE

Joined Jan 6, 2017
13
Hello

I am studying one of my teacher lecture and i read that
in the Principle of Superposition:

With dependent sources, superposition can be applied when
control functions are external to the network containing the
sources.

but i couldn't understand it could you explain it with examples ?

#### RBR1317

Joined Nov 13, 2010
674
The method of superposition is to consider the contribution of each source independently. That is why only one source is active at a time while the other sources are zeroed. So how could a dependent source be considered independently?

Thread Starter

#### SUN SHINE

Joined Jan 6, 2017
13
i understand this thing but i am asking abut the condition that the superposition principle can be applied as mention above
The method of superposition is to consider the contribution of each source independently. That is why only one source is active at a time while the other sources are zeroed. So how could a dependent source be considered independently?

#### RBR1317

Joined Nov 13, 2010
674
With the superposition method, the final answer is the addition of the contribution from each source. But with a dependent source one would need the final answer to get the control function in order to get the final answer (unless the control function was itself independent). But if you can get around that dichotomy, would the method still be considered superposition?

Thread Starter

#### SUN SHINE

Joined Jan 6, 2017
13
But with a dependent source one would need the final answer to get the control function in order to get the final answer (unless the control function was itself independent). But if you can get around that dichotomy,

I'm sorry if i am disturbing you

could you just give an example or rephrase your replay with simpler words

#### RBR1317

Joined Nov 13, 2010
674
If the control function is external to the network being analyzed, then the dependent source will appear as a constant source for the purposes of analyzing the network via superposition. Can you provide an example of correctly solving a circuit with a dependent source via superposition wherein the control function is not external?

#### MrAl

Joined Jun 17, 2014
8,556
Hello

I am studying one of my teacher lecture and i read that
in the Principle of Superposition:

With dependent sources, superposition can be applied when
control functions are external to the network containing the
sources.

but i couldn't understand it could you explain it with examples ?
Hi,

This question is obviously not worded correctly. That's because dependent sources are dependent on other places in the network itself, and certainly would not have to have dependence on external stimuli.

What the 'author' must have meant was that 'external' means external to the dependent sources themselves, such that if shorting out one dependent source kills another dependent source's stimulus then you cant short out that source, or something like that.

The problem with "shorts" in circuit analysis is that they are never defined properly. Sometimes we short something for the analysis but it's not the same thing as a zero ohm short. A 'short' in the analysis procedure often plays a dual role where for current it is a common everyday short but for voltage it is an open circuit not a true short. There could be other variations as well because these are topological 'tools'.

To understand this better we could look at a few networks with dependent voltage sources to keep it simple.

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