What is the power output in kW for this measurement?

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Discussion Overview

The discussion revolves around calculating the power output in kilowatts (kW) based on measurements taken from a watt-hour meter during a lab experiment. Participants are exploring the relationship between the number of revolutions of the meter dial, the time taken for those revolutions, and the resulting power output.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant states the formula for power based on their measurements: Power = (3600s/hr) / (146s) * (10/400) * 1kWh = 0.62069 W.
  • Another participant questions the interpretation of the time measurement, asking for clarification on whether it refers to 10 revolutions in 146 seconds or 146 revolutions in 10 seconds.
  • A later reply suggests that the power output should be 0.62069 kW, indicating a possible correction from the initial calculation.
  • Another participant calculates a different value of 0.6164 kW using a similar approach, providing an alternative method for the calculation.
  • There is a clarification on the relationship between kWh and kW, explaining that 1 kWh equals power (kW) multiplied by time (hours), and that 1 kWh is equivalent to 3600 kJ.

Areas of Agreement / Disagreement

Participants express differing calculations for the power output, with one suggesting 0.62069 kW and another calculating 0.6164 kW. The discussion remains unresolved regarding which calculation is correct.

Contextual Notes

There are potential limitations in the assumptions made about the time measurement and the interpretation of the watt-hour meter readings, which could affect the calculations presented.

Inquiring_Mike
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Homework Statement


We used a watt-hour meter in a lab, 400 revolutions of the dial = 1kWh. We measured the time for 10 revolutions of the dial ( in seconds).
How would I calculate the power?

Time for 10 revs = 146s

Homework Equations


The Attempt at a Solution


Power = (3600s/hr) / (146s) * (10/400) *1kWh = 0.62069 W ?
 
Last edited:
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Does one mean Time for 10 revs = 146s or 146 revs in 10 s?
 
Sorry... fixed :)
 
... After some more thinking...I think it should be 0.62069 kW. Would this be correct?
 
Any help would be very much appreciated... :)
 
Inquiring_Mike said:
... After some more thinking...I think it should be 0.62069 kW. Would this be correct?

Yes, but I calculate 0.6164 kW.

Take (1 kWh)/(400 revs)*(10 revs/ 146 s) * 3600 s/h = ______ kW.

The unit kWh is simply power (kW) * time (hours) = energy. 1 kW-s = 1 kJ, so 1 kWh = 3600 kJ.
 

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