Question

If an automobile had a 100%-efficient engine, transferring all of the fuel’s energy to work, would the engine be warm to your touch? Would its exhaust heat the surrounding air? Would it make any noise? Would it vibrate? Would any of its fuel go unused? Discuss.

Answer 1

If a 100%-efficient engine transfers 100% of the fuel's energy to work then, 0% of the fuel's energy would be wasted as heat, vibration, or otherwise.

If it extracts 100% of the available energy from the fuel then anything left will have 0% available energy; that will not be fuel.

Where can we find such an engine?