why voltage across current source can't be measured?

why voltage across current source can't be measured?

chirag_kotadia

Member

Updated: Oct 26, 2024

Views: 1.8K

Hi frenz
I'm bit confused about the concepts of voltage n current source... Can u answer why voltage across current source & current from voltage source can not be measured?? 😔

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harshul.lath

Member • Jun 6, 2010

frnd i think your question is wrong we can measure voltage across current source and current fron a voltage source

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rohit bisht

Member • Jun 6, 2010

I think we can't measure voltage from current source because there is no voltage drop across current source . correct me if i'am wrong.

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harshul.lath

Member • Jun 7, 2010

well i think we can let say a transistor it is an current souce n we can measure voltage across it.....

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chirag_kotadia

Member • Jun 7, 2010

rohit bisht
I think we can't measure voltage from current source because there is no voltage drop across current source . correct me if i'am wrong.
But why?? Plz answer

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shakir414

Member • Jun 7, 2010

my logic is that the current is the flow of electrons,so when a voltage is applied across a current source the amount or the force of the current is very large compared to a voltage.so we cant measure the the voltage across a current source.correct me if am wrong.

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chirag_kotadia

Member • Jun 8, 2010

shakir414
my logic is that the current is the flow of electrons,so when a voltage is applied across a current source the amount or the force of the current is very large compared to a voltage.so we cant measure the the voltage across a current source.correct me if am wrong.
Shakir, pardon me.
I'll correct your statement. In measurement of voltage across current source, We are not applying voltage, indeed we are putting voltmeter across current source. So try again to answer.😁

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Saandeep Sreerambatla

Member • Jun 8, 2010

rohit bisht
I think we can't measure voltage from current source because there is no voltage drop across current source . correct me if i'am wrong.
This is correct if you consider your current source as Ideal one , but practically Ideal sources does not exist! Thus we can measure it

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sai krishna

Member • Jun 9, 2010

I didn't get your question well,but wat i can support is current sources are connected in series with the load and voltage sources across the load,as voltages can be measured across open circuits and current over short circuit that passes through conductor.

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reachrkata

Member • Jun 20, 2010

Before I tell you what I want to tell, let me first confirm that, yes, we can measure the current through a voltage source. Just connect an ammeter in series to it.

I think we can't measure voltage from current source because there is no voltage drop across current source . correct me if i'am wrong.
I don't agree to this argument. In fact there is a voltage. Consider a simple circuit diagram of a current source (I) connected to a resistor (R). Now the resistor will have a potential of V=IR. Now if KVL has to be obeyed in this circuit, V will also be the voltage across the current source. So the so called ideal current source also has a voltage drop.

Actually speaking, there doesn't exist any physical device called a current source. I mean you can't find a simple device for a current source, like there a battery for a voltage source. All so called current sources are in fact voltage sources with special feedback circuits to ensure that the current it supplies to any load connected to it is constant, irrespective of the load value. The current source is simply an analytical replacement for such a special circuit, which is used to simplify circuit analysis.

Going by this logic too, since a current source is actually a specialized voltage source, it should have a voltage drop.

- Karthik
😁

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lal

Member • Jun 22, 2010

I agree with Karthik that there is no any so called current source. In that case can we just connect a current source to a resistor? It would be a voltage source delivering a constant current i guess. There should ofcourse be a potential difference for a current to flow.

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shreyasm89

Member • Jun 25, 2010

..Voltage sources and current sources are all energy devices.Current source is a theoretical concept which says that it supplies a constant current in the branch in which it is connected. First of all we assume that a current source is always an IDEAL one. Otherwise the entire concept of current source will break down. Remember there is no difference in the values of currents at the i/p and o/p of a current source. this implies that there is no internal resistance of the current source. Voltage sources are meant to create potential diff. between the points they are connected and hence voltage can be measured across them.Current sources simply imply that a particular value of current flows in that branch. that is why we consider current sources as short while applying KVL to a particular ckt. Hence we can measure current in the current source but not voltage because it would mean measuring voltage across two points at same potential

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Mr.Don

Member • Jun 27, 2010

saaki
I didn't get your question well,but wat i can support is current sources are connected in series with the load and voltage sources across the load,as voltages can be measured across open circuits and current over short circuit that passes through conductor.
You rock Saaki..the best answer for the question so far.😀

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reachrkata

Member • Jun 27, 2010

shreyasm89
.. Remember there is no difference in the values of currents at the i/p and o/p of a current source. this implies that there is no internal resistance of the current source.
Whoa you got it wrong there buddy. Having the same input and output current doesn't mean no internal resistance (i.e. a short). In fact its having the same input and output voltage which means a short.
Consider a resistor through which a current is flowing. Even though the current into the resistor and out of it are the same, it does have a voltage drop.

shreyasm89
..Current sources simply imply that a particular value of current flows in that branch. that is why we consider current sources as short while applying KVL to a particular ckt. Hence we can measure current in the current source but not voltage because it would mean measuring voltage across two points at same potential.
In fact when you apply KVL you will realise that a current source cannot be a short (as I explained in my previous post).

-Karthik

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shreyasm89

Member • Jun 27, 2010

reachrkata
Whoa you got it wrong there buddy. Having the same input and output current doesn't mean no internal resistance (i.e. a short). In fact its having the same input and output voltage which means a short.
Consider a resistor through which a current is flowing. Even though the current into the resistor and out of it are the same, it does have a voltage drop.

In fact when you apply KVL you will realise that a current source cannot be a short (as I explained in my previous post).

-Karthik
oops! sorry der....yeah i realised my mistake.KVL cannot be applied in cases of current souces.But we do assume a current source to be ideal don't we?

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reachrkata

Member • Jun 28, 2010

Yes for analysis, it can be assumed ideal.
For current sources, the ideal scenario is that its internal shunt resistance is infinite. Thats all. The source as such remains the same for ideal or non ideal scenarios.

- Karthik

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anandchavan123

Member • Jun 28, 2010

because there is no voltage drop across the current source.

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aj_onduty

Member • Aug 25, 2010

chirag_kotadia
Hi frenz
I'm bit confused about the concepts of voltage n current source... Can u answer why voltage across current source & current from voltage source can not be measured?? 😔
Dear friend, I believe you want to stress on the word "can't ".
We can't measure the voltage across the current source because your teacher blindly believes on the fact that "Are you crazy? Why in the world there is a need to measure voltage across a current source. No, u can;t do it(as if it were a taboo.😉)."
I have faced this same thing dear friend, in my practical classes. And yes, I have felt pretty stupid to do my practicals under that instructor. But we can measure the voltage. It is allowed. There is a potential drop across. Sadly, I couldnt measure it, as the instructor won't leave from my table(I was kind of a bit too nosy about things.).
I think my answer satisfies u.

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swapnakumar

Member • Aug 25, 2010

chirag_kotadia
Hi frenz
I'm bit confused about the concepts of voltage n current source... Can u answer why voltage across current source & current from voltage source can not be measured?? 😔
an ideal voltage source has a resistor in series with it and using ohm's law i=v/r u can calculate current similarly you can calculate volate using kvl in a current sorce wtih a resistor in parallel

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waqar ahmed

Member • May 13, 2015

current source is not practically exist this is ideal source we can transform current source into the voltage source by source transformation. voltage across the current source is exactly exist because there is no voltage this mean that there is no current if current in any branch then this meant that voltage must be in branch because we know that if potential difference between two point this cause of current flow....
simply we say that if voltage is exist between two point then current flow other wise no current..

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