1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Heat Engine

  1. Jan 13, 2016 #1
    I have read that when we directly use 'W' Joules of electrical energy to heat a liquid,the maximum heat we can use to heat the liquid is W.
    However, when we use a heat pump Q=[COP+1]*W , and that means Q > W. Hence heat pump is more efficient and is preferred over electrical heater. Doesn't this violate conservation of energy..i.e give W joules of work and get equivalent heat of More than W
  2. jcsd
  3. Jan 13, 2016 #2


    User Avatar

    Staff: Mentor

    No. A heat pump doesn't "directly" heat something it just moves heat to where we want it from somewhere else. If you account for what happens on both ends, you'll see that the net thermal energy change is exactly equal to W.
  4. Jan 13, 2016 #3
    So in a way it cause a minute change in temperature of the atmosphere right? (or from the source of heat). So we extract heat Q1 from atmosphere, do work W, hence heat we supply to sink is Q1+W?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook