Calculate percentage change in heat output

  • #1

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:

Answers and Replies

  • #2
374
1
Find the resistance of the heater. Use that value of resistance and 110 volts to find new power output. %=(initial-finial)*100/initial
 
  • #3
Thanks thats great! I've done it now
 
  • #4
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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