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iloveanatomy iloveanatomy
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11 years ago
Because voltage is zero, the power delivered by it would be zero. But it would still affect the rest of the circuit right? Or would you model it with an open/short circuit? If it's not delivering any power, how can it be producing a current?
What about for a voltage source with no current through it?
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#1
11 years ago
voltage is energy per charge. if charges are moving through it they have kinetic energy, but if each charge doesn't have a noticeable amount of energy then power is negligible. a voltage source with no current has no power, since an energy per charge times no charge is 0.
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#2
11 years ago
An ideal current source will deliver the current it's designed to supply. Stop thinking of it in terms of voltages, it's a current source not a voltage voltage source. If there is zero impedance across it then it will happily deliver the current. If the impedance across it increases then the current remains the same but a voltage will occur across the impedance (V = I*R) if R=0 the V=0 but that doesn't affect the current source.

Thevenin's theorem allows you to model both voltage sources and current sources in terms of the other. So a voltage source can be modeled as a current source and vice-versa.

"voltage is energy per charge"

Really it's not, the amount of energy an electron has is  meaningless concept. An electron has charge, that's it (for the purposes of this question)

"If charges are moving through it they have kinetic energy"

Well it might be true but has nothing to do with the question

"if each charge doesn't have a noticeable amount of energy then power is negligible"

So what is the energy of an electron? The concept is meaningless in terms of the question. An electron gains energy when an atom absorbs a photon and it moves to a higher energy level. This has got nothing to do with the question.

"a voltage source with no current has no power" We're discussing current sources though

"since an energy per charge times no charge is 0." word salad

ETA

You were right when you said you didn't understand

" if a switch is closed, there is no current from one side of the switch to the other -- and the light is on"

Total nonsense.

"Your question is good. You need to learn more about voltage and current before you start working on stuff or else you will get shocked!"

It's about MODELLING nothing at all to do with getting shocked. Geez,I hardly think you are qualified to judge whether or not it's a good question.
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#3
11 years ago
I am not exactly understanding what you are asking.

For example, if a switch is closed, there is no current from one side of the switch to the other -- and the light is on.  If the switch is open, there is voltage across the switch -- and the light is off.  There is current there in both situations.

Measuring voltage is totally different from measuring current.  When you measure voltage, you are measuring it "across" something like a switch or plug; when you measure current, you are measuring it "along" something like a wire.  

Your question is good.  You need to learn more about voltage and current before you start working on stuff or else you will get shocked!
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buglovebuglove
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#4
11 years ago
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#5
11 years ago
I assume you are asking about a constant current supply with no voltage output = the load resistance is zero or the current source is not functioning.
Constant voltage is the usual design. The voltage is very likely still there even if no current is being supplied.
Neither zero voltage nor zero current affect the rest of the circuit unless the circuit changes so that the voltage or current is other than zero.
Zero is an ideal which we often approach very closely, but do not reach exactly = we can have current flow though approximately zero resistance, even though the delivered power is approximately zero. Similarly the the voltage does deliver infinitesimal amount of power even if the load resistance is a google ohms.    Neil
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