Is this a short circuit or not?

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Homework Help Overview

The discussion revolves around a circuit involving a capacitor, a switch, and a voltmeter. The original poster is trying to understand whether a current flows through the voltmeter when measuring the voltage across a charged capacitor and if this situation constitutes a short circuit.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the implications of the voltmeter's high resistance on current flow and voltage readings. Questions about the definition of a short circuit and the typical resistance associated with it are also raised.

Discussion Status

Some participants suggest that the voltmeter's high resistance prevents significant current flow, while others note that a small current may still pass through it. The conversation is exploring different interpretations of how the voltmeter interacts with the circuit without reaching a definitive consensus.

Contextual Notes

There is an ongoing discussion about the ideal versus real behavior of voltmeters, including the assumptions made about their resistance and the effects on the circuit being measured.

Phyba
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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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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:
 
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.
 
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).
 
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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