Grade 9 Power Problems (Watts/kWh, power rating question)

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SUMMARY

The discussion focuses on calculating energy consumption using power ratings, specifically a hot plate with a power rating of 1250 Watts. The user successfully converted Watts to Kilowatts, calculating energy usage over 3 hours as 3.75 kWh. However, confusion arose regarding the units of energy, as the user initially believed energy should be expressed in Joules or Kilojoules. The conversion from kWh to Joules is clarified, establishing that 1 kWh equals 3.6 million Joules.

PREREQUISITES
  • Understanding of power ratings (Watts)
  • Knowledge of energy units (Kilowatt-hours, Joules)
  • Familiarity with basic physics equations (E=Pt)
  • Ability to perform unit conversions
NEXT STEPS
  • Learn about energy conversion formulas, specifically from kWh to Joules.
  • Study the relationship between power, energy, and time in physics.
  • Explore practical applications of power ratings in household appliances.
  • Investigate the significance of energy efficiency in electrical devices.
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Students studying physics, educators teaching energy concepts, and anyone interested in understanding power consumption and energy calculations.

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Homework Statement



So, i need to learn how to do questions with finding out the power rating, and energy etc etc from using the triangles given and i am having some trouble since some of my triangles are missing and i need some help with converting.


Homework Equations



1) A hot plate has a power rating of 1250 Watts. How much energy in Kilowatt-hours is used when this hot plate is used for 3.00 hours at a banquet?


The Attempt at a Solution



I converted the watts to kWh so i turned 1250 to 1.25. On the triangle with the variables of "P," "E," and "T," it says E=Pt So i did 1.25*3 and got 3.75kWh.
The problem is that i thought that "E" was always in joules or Kilojoules so i do not think the answer can be 3.75kWh since that is the power rating.
If i am correct, i need help with converting the 3.75kWh into joules if that is what i need to do.

Thanks !
 
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1 Watt = 1 Joule/second
1 Watt*hour = (1 Joule/second)*3600 seconds = 3600 Joules
1 kWh = 1000 Watt*hour

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