1. The problem statement, all variables and given/known data So I am doing a mini-lab and I measured the temperature of water before heating it up and after. I determined delta T or the temperature gain to be https://www.physicsforums.com/file:///C:/Users/BADGER~1/AppData/Local/Temp/msohtmlclip1/07/clip_image002.gif [Broken]=20.555https://www.physicsforums.com/file:///C:/Users/BADGER~1/AppData/Local/Temp/msohtmlclip1/07/clip_image004.gif [Broken] Now it states to calculate the efficiency of the heat-transfer process asuuming the power outuput of the oven is 1000W. 2. Relevant equations E=P xt 3. The attempt at a solution I was thinking about calculating the energy output which is 30,000 J Then use the definition of a calorie. Not sure if there is an equation for this or not. It is the delta T or temperature gain multiplied by the amount of liters which is 0.250 L. The energy input is 5.139 Calories and converting that to joules is 21501.576 J. Then you subtract the two for the energy efficiency. Is this correct? Someone said to use this equation: Q=mCΔT I don't have a mass. Which way is correct? Am I on the right track or not?