Power of a Sine Wave: Formula to Calculate W

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Discussion Overview

The discussion revolves around the formula for calculating the power (W) of a sine wave electrical signal traveling through a wire, considering parameters such as frequency, voltage, and current. The scope includes theoretical aspects of electrical power, the impact of load types, and the implications of frequency on power calculations.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Jason O inquires about the formula for calculating power in a sine wave electrical signal, mentioning frequency, voltage, and current.
  • One participant notes the necessity of knowing the phase angle and suggests that R_wire is needed if the focus is on power consumption.
  • Another participant states that if voltage and current are in phase (indicating a purely resistive load), power can be calculated simply as P = V * I, regardless of frequency.
  • Jason O questions whether power remains the same across different frequencies for the same voltage, referencing a claim that doubling frequency quadruples power.
  • A participant refutes Jason O's claim, asserting that wave shape affects power and that frequency's significance arises primarily due to the skin effect at high frequencies.
  • Another participant suggests that P = V * I does not apply in the context of coils, indicating a more complex relationship in such scenarios.
  • Links to external resources are shared for further reading on power in AC circuits.
  • A participant comments on the complexity of square waves, noting that they consist of multiple sine wave frequencies, which can complicate power calculations in inductive circuits.
  • There is a suggestion for Jason O to consider using a function generator for producing sine waves.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between frequency and power, with some asserting that frequency does not affect power in purely resistive loads, while others highlight the importance of wave shape and the skin effect. The discussion remains unresolved regarding the implications of frequency on power calculations.

Contextual Notes

There are limitations regarding assumptions about load types (resistive vs. inductive) and the effects of frequency on power calculations, which are not fully explored in the discussion.

Jdo300
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Hello,

What is the formula to calculate the power (W) of a sine wave electrical signal traveling through a wire if I know the frequency, voltage, and current?

Thanks,
Jason O
 
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You need to know the phase angle.
Unless you just want to know how much power the wire is consuming.
In which case you need R_wire.
 
If the voltage and current are in phase (your load is resistive only), then the power is just P = V * I, independent of frequency.
 
berkeman said:
If the voltage and current are in phase (your load is resistive only), then the power is just P = V * I, independent of frequency.

So you are saying that a wire carrying 100 volts at 60Hz has the same amount of power as a wire carrying 100 volts at 120Hz or 1kHz (assuming the same load in all three cases)? I heard somewhere that if you double the frequency of the wave, that the power is 4 times as much, is that true?

Thanks,
Jason O
 
No, it's not.
Wave shape will make a difference in power.
Frequency only becomes important (if the load is resistive) as it gets high enough for the skin effect to make a significant contributation.

Since you seem primarily interested in coils then note that P=V * I does not apply to what you are doing.
 
Nice pages es1.
Since the OP seems to be contemplating square waves the page 2 doesn't really apply to him.

A square wave reflects the sum of a large number of
different frequency sine waves.
This can be tricky in inductive circuits.

Perhaps Jdo should coinsider geting a function genenerator that can produce sine waves.
 

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