Calculate percentage change in heat output

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Homework Help Overview

The discussion revolves around calculating the percentage change in heat output of a heating unit when the voltage supply changes. The subject area includes electrical power and resistance concepts.

Discussion Character

  • Exploratory, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss using the formula for resistance and power to determine the new power output at a lower voltage. There are attempts to clarify the steps needed to calculate the percentage change in heat output.

Discussion Status

Some participants have provided guidance on calculating resistance and power output, while others have shared their results. There is a mix of interpretations regarding the calculations, but no explicit consensus has been reached.

Contextual Notes

Participants mention the context of being students in the UK and express interest in the relevance of online exam solutions, indicating a broader discussion about educational resources.

physicist93
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Homework Statement


A 500W heating unit is designed to operate on a 115V line. If the line voltage drops to 110V, calculate the percentage drop in heat output.

Homework Equations


R=V^2/P

The Attempt at a Solution


P=V^2/R

Use V=115, then use V=110, use Power P=500...but not sure how

p.s. I am a UK Physics student. I was wondering could you also say whether you are in the UK or US or...
 
Last edited:
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Find the resistance of the heater. Use that value of resistance and 110 volts to find new power output. %=(initial-finial)*100/initial
 
Thanks that's great! I've done it now
 
I got an answer of 8.5%! sounds right...

Btw what do people think about the questions on online-exam-solutions?
 

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