Can Resistors Receive Power on an Open Circuit?

In summary, the conversation discusses the concept of power delivered to resistors on an open circuit. While the formula P=IV is commonly used, it is important to note that it is only valid when there is current flowing through the resistor. In the case of an open circuit, there is no current, thus no power is being delivered. The formula (V^2)/R should be used instead, but it is important to understand that the V in this formula represents the voltage difference across the resistor, which is zero when there is no current. Overall, the main point is that an open circuit means no current, and therefore no power is being delivered to the resistors.
  • #1
jedjj
26
0
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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  • #2
What is the current through an open circuit?
 
  • #3
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.
 
  • #4
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.
 
  • #5
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.
 
  • #6
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.
 
  • #7
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.
 

1. What is power delivered to resistors?

The power delivered to resistors is the amount of energy that a resistor uses or dissipates as heat when current flows through it. This power is measured in watts (W) and is calculated using the formula P = I²R, where I is the current flowing through the resistor and R is the resistance of the resistor.

2. How is power delivered to resistors affected by changes in resistance?

The power delivered to resistors is directly proportional to the resistance of the resistor. This means that as the resistance increases, the power delivered also increases. Similarly, as the resistance decreases, the power delivered decreases. This relationship is described by the formula P = V²/R, where V is the voltage across the resistor.

3. Is the power delivered to resistors the same as the power supplied by a voltage source?

No, the power delivered to resistors and the power supplied by a voltage source are not the same. The power supplied by a voltage source is the total amount of energy that is provided to the circuit, while the power delivered to resistors is the amount of energy that is used or dissipated by the resistors in the circuit.

4. How does the power delivered to resistors affect the temperature of the resistors?

The power delivered to resistors is converted into heat energy, which can cause the temperature of the resistors to increase. This increase in temperature can impact the performance of the resistors and may even cause them to fail if the power delivered is too high for the resistor to handle.

5. Can the power delivered to resistors be controlled?

Yes, the power delivered to resistors can be controlled by changing the voltage or current in the circuit. This can be done by using a variable resistor or by adjusting the voltage or current from the power source. By controlling the power delivered to resistors, you can prevent overheating and potential damage to the resistors in the circuit.

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