Which of these is an experiment generally regarded as being first carried out by james joule?

observing that objects increase in temperature when heated with fire

showing that friction slows down the motion of objects

measuring the temperature increase of water from doing work stirring it

testing the mechanical advantage of pulleys

what did joule's experiment directly show?

the temperature of water increases from the addition of heat.

heat is a form of energy.

heat can be neither created nor destroyed.

electromagnetic radiation has energy