Energy can be changed into different forms. In the interactive exhibit (shown in the image above), winding the handle puts in mechanical energy which is converted into electrical energy, shown by the lamp. page 1 of 10

What was Joule's most important contribution to science?

Joule had carried out earlier experiments exploring the relationship between electricity and work. He then began looking at the relationship between other forms of energy.

He showed that the rise in the water temperature was caused by the paddlewheel moving the water molecules, therefore causing them to rub against one another. This friction produced heat energy, shown on the thermometer. By altering the weights connected to the paddlewheel, and the length of the drop, he was able to put a numerical value on the relation between heat and mechanical work.

However, because Joule had a large range of results, he attempted to get a more accurate value by experimenting on the friction of solid bodies and gases. He continued his research for over thirty years until other scientists were finally persuaded of the validity of the single 'unique' constant'.