Calculating Watt Hours for a time interval less than 1 second

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Discussion Overview

The discussion revolves around the calculation of watt-hours for time intervals less than one second, specifically addressing the validity and interpretation of results from an online physics calculator. Participants explore the implications of using very short time intervals in energy calculations, including unit conversions and the correctness of the output.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants express confusion regarding the output "J watts hours" and question its validity as a unit.
  • There is a request for a manual calculation of energy using the formula Power x Time, specifically for 10W over 0.01 seconds, with results expressed in watt-hours.
  • One participant notes that the online calculator initially indicates a negative value for inputs less than one second, but this message disappears and the calculation proceeds.
  • Another participant emphasizes that watt-hours should represent energy and discusses the relationship between power, time, and energy.
  • A calculation is presented, converting joules to watt-hours, showing the process of unit conversion from W*s to W*hr, but it is noted that this did not fully address the initial question posed.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of the output from the calculator or the validity of using time intervals less than one second in these calculations. Confusion remains regarding the units and the correctness of the numerical results.

Contextual Notes

There are unresolved questions about the implications of using very short time intervals in energy calculations, as well as the accuracy of the units provided by the online calculator. The discussion reflects a lack of clarity on how to properly express and interpret energy calculations in this context.

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TL;DR
Is it OK to put less than 1 second into the equation ?
I use an online physics calculator a lot to help me for various reasons. When I input less than 1 second into a watt hour calculation it initially tells me it can not be a negative value although that does disappear and it does do the calculation.

Example power 10 w time 0.01 seconds 0.1 J watts hours.
 

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pete94857 said:
Example power 10 w time 0.01 seconds 0.1 J watts hours.
I have no idea what a "J watts hours" is as a unit, and the number 0.1 looks incorrect to me.

Can you show us by hand how you would calculate 10W*0.01s with the results in Watt*Hours?
 
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berkeman said:
I have no idea what a "J watts hours" is as a unit, and the number 0.1 looks incorrect to me.

Can you show us by hand how you would calculate 10W*0.01s with the results in Watt*Hours?
It is an ambiguous interface. The answer is in joules.
 
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pete94857 said:
TL;DR Summary: Is it OK to put less than 1 second into the equation ?

I use an online physics calculator a lot to help me for various reasons. When I input less than 1 second into a watt hour calculation it initially tells me it can not be a negative value although that does disappear and it does do the calculation.

Example power 10 w time 0.01 seconds 0.1 J watts hours.
It doesn’t like zero, but greatery than zero seems ok. Watt-hours should be Energy.
 
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berkeman said:
I have no idea what a "J watts hours" is as a unit, and the number 0.1 looks incorrect to me.

Can you show us by hand how you would calculate 10W*0.01s with the results in Watt*Hours?
Power x time = Energy. Power is the required energy to power something, time is the amount of time needed and energy is the energy needed to perform the task at that time. Or reverse E/t=w
 
pete94857 said:
Power x time = Energy. Power is the required energy to power something, time is the amount of time needed and energy is the energy needed to perform the task at that time. Or reverse E/t=w
Well, that didn't really answer my question, but I'll show you how to do it since I don't think this is a schoolwork-related question.

So to calculate the Energy based on power and time and convert units from W*s to W*hr:

$$E = 10W ~0.01s ~ \frac{1hr}{3600s} = 27.8\mu Whr $$

Note how I converted from W*s (Joules) to W*hr by multiplying by "1" in this form: ##1=\frac{1hr}{3600s}## to get the right cancellations of units from the initial answer to what I wanted. :wink:
 
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