Is this a short circuit or not?

In summary, the conversation is discussing the behavior of a circuit with a charged capacitor and a voltmeter connected to its terminals. The question is whether a current flows through the voltmeter and if it could cause a short circuit. It is explained that an ideal voltmeter has infinite resistance and therefore no current flows through it. The voltmeter will read the voltage across the capacitor and will not cause a short circuit. The difference between a short circuit and a usual electric resistance is also clarified.
  • #1
Phyba
9
0
My doubt is about the circuit in the picture. The capacitor is charged ans the switch open. There's a voltimeter connected to the terminals of the capacitor.

Does a current flow through the wires of the voltimeter causing a short circuit? If not, what would happen in the circuit described? What would the voltimeter read??

I would really like to understand it.

Thank you very much!
 

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  • #2
Well, actually it could never be a short circuit beacuse the voltimeter has a very high resistance, right? So there is a current and the voltimeter would read 0?

:confused::confused:
 
  • #3
An ideal voltmeter presents an infinite impedance (resistance) to what it's measuring, so no current can flow through it. It's as if the voltmeter could "see" the voltage without ever touching the circuit in any way.
 
  • #4
Phyba said:
Well, actually it could never be a short circuit beacuse the voltimeter has a very high resistance, right? So there is a current and the voltimeter would read 0?

:confused::confused:

What is a short circuit? What is the usual electrical resistance through a short circuit?

As you say, the voltmeter is designed to have a very high resistance, ideally taken as infinite. Ideally, the current through the voltmeter is zero, but in reality there is a very small current passing through it (necessary for the needle to swing to register the voltage across its terminals). But the current is low enough that you can generally consider it not to affect the charge on the capacitor (even if it discharges very slightly through the voltmeter).
 
  • #5
Phyba said:
Well, actually it could never be a short circuit beacuse the voltimeter has a very high resistance, right? So there is a current and the voltimeter would read 0?

:confused::confused:

Yes the Voltimeter has a very high resistance so there will be a very small current. The voltimeter will not read zero. It will read the voltage at the capacitor. That's why it's called a voltimeter.
 
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