Can Resistors Receive Power on an Open Circuit?

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Discussion Overview

The discussion revolves around the concept of power delivered to resistors in an open circuit scenario. Participants explore the implications of having resistors in a circuit where no current flows, examining the relationships between voltage, current, and power using various formulas.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • The original poster questions whether power can be delivered to resistors on an open circuit, referencing the formulas P=IV and P=(V^2)/R.
  • One participant asserts that in an open circuit, there is no current, leading to zero power delivery, and emphasizes that power dissipation requires current flow.
  • Another participant explains that the formula P=(V^2)/R assumes current is present, and thus is not applicable in the case of an open circuit.
  • It is noted that an open circuit implies infinite resistance, resulting in no current and consequently no power.
  • One participant clarifies that while V^2/R suggests power could exist, the voltage across the resistor is zero when there is no current.
  • The original poster acknowledges understanding that current is zero in an open circuit and expresses gratitude for the clarifications provided by others.

Areas of Agreement / Disagreement

Participants generally agree that in an open circuit, no current flows, leading to no power delivered to the resistors. However, there is some discussion regarding the interpretation of the power formulas in this context.

Contextual Notes

Participants discuss the limitations of applying power formulas without current, highlighting the dependence on the definitions of voltage and current in the context of resistors in an open circuit.

jedjj
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A question on my homework is asking about power delivered to resistors. These resistors are on an open circuit. While P=IV, it is also equal to (V^2)/R, so my question is if resistors are on an open circuit is it possible for power to be delivered to them? There is a source supplying voltage to the circuit.

Thanks in advance

[edit]:Move this thread if necessary-no this is not actually a question on my homework, but rather a confusion of mine about how to approach the problem.
 
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What is the current through an open circuit?
 
If the resistors are open circuited, charge is not flowing (indeed, cannot flow) through them. In other words, there is no current. If the current is zero, what happens to P? This should be pretty intuitive. You're not going to dissipate energy by...doing nothing.

The formula P = V2/R is derived by assuming that the current in the resistor is V/R (which is true for a resistor that happens to obey Ohm's law). In which case, P = IV = (V/R)V = V2/R.

In other words, this formula is, very specifically, "the power dissipated in a resistor of resistance R with voltage V across it." It is not valid under any other circumstances.

Edit: DaleSpam was much more succinct than I. I hope he's not mad that I gave away this answer. This is not a homework thread. The OP was confused about a concept, so I clarified it. That having been said, I can see the value of asking the OP pointed questions in order to allow him to reason his way to the answer himself.
 
If the circiut is open then current is 0. If the current is 0 then so is the voltage drop across the resistor. Power is the same using either relationship.
 
An open circuit means an infinite resistance so no current. No current = no power.
What confuses a lot of students is the V^2/R, it seems to say you should have power with no current. But the V is the voltage DIFFERENCE across the resistor. If there is no current through the resistor then there is no voltage difference across it and so V is zero.
 
Thank you, I am aware that the current through an open circuit is zero, and assumed that the (V^2)/R method is there when there is current assumed to be through it, but I was unsure. So I thank you for your help.
 
cepheid said:
DaleSpam was much more succinct than I. I hope he's not mad that I gave away this answer.
Not at all, that was pretty fun to see all of the replies in such a short time.
 

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