A heat engine does 200 J of work per cycle while exhausting 400 J of waste heat. What is the engine's thermal efficiency?

Video transcript

Hey, everyone. So this problem is dealing with heat engines. Let's see what it's asking is the dynamo on a bicycle generates electricity as we pedal. The dynamo has a per cycle work output of 50 drools and a heat waste heat output of 80 Jews. We're asked to determine the dynamo's thermal efficiency during that bike ride. Our multiple choice answers are a 0.65 B 0.24 C 0.38 or D 0.87. So to find the thermal efficiency, we need to recall the equation for thermal efficiency, which is a, is equal to the work divided by our total heat. And so the work, how good is 50 jewels from the problem? And our total heat output is going to be that 50 jewels plus our waste heat, which is 80 jewels. And so we plug that into our calculator and we get 0.38. So that's an efficient C of 38%. And that aligns with the answer choice C that's all we have for this one. We'll see you in the next video.