Electric Potential: Resistor, Battery, Voltmeter - What is the PD?

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Discussion Overview

The discussion revolves around the concept of potential difference (p.d.) in an incomplete electrical circuit involving a resistor, a battery, and a voltmeter. Participants explore the implications of connecting a voltmeter across a resistor when the circuit is not complete.

Discussion Character

  • Conceptual clarification, Debate/contested, Technical explanation

Main Points Raised

  • One participant questions the potential difference across a resistor connected to a battery with an incomplete circuit, asking whether it is zero or 5V.
  • Another participant asserts that the p.d. across the resistor is zero, explaining that potentials are relative and that the potential at the resistor's positive terminal is the same as the battery's positive terminal.
  • A further contribution references Ohm's Law, stating that since current cannot flow in an incomplete circuit, the voltage across the resistor must be zero, but notes that the potential from the open end of the resistor to the wire connected to the negative terminal is 5V.

Areas of Agreement / Disagreement

Participants express differing views on the potential difference across the resistor, with some asserting it is zero and others suggesting it is 5V relative to the wire connected to the negative terminal. The discussion remains unresolved regarding the interpretation of potential difference in this context.

Contextual Notes

Participants rely on assumptions about circuit completeness and the definitions of potential difference, which may affect their conclusions. The discussion does not resolve the implications of these assumptions.

Kushal
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hi...

if you got resistor, having its positive terminal attached to the positive end of a battery (say emf 5V), and the negative end left connected to a simple wire, as such...in short, the circuit is not complete.

what is the pd when a voltmeter is connected across the resistor?

is it zero, or 5V??

and what is the potential, at any point on the wire connected to the negative terminal of the resistor?

thnks
 
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The p.d. is zero. Potentials only make sense relatively. In this case, the potential is the same as the +ve end of the battery.
 
oooiee...thnks
 
Ohm's Law: V=IR
V = voltage across resistor
I = current through resistor
Current cannot flow since the circuit is incomplete (Kirchoff's Current Law).
I = 0,
regardless of R, V = 0
The p.d. across the resistor is zero, but the p.d. from the open end of the resistor to the "simple wire" is 5V.
 

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