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Why and when was the Joule adopted as the SI unit of energy?

The British Association proposed the use of Joule's name for the international, or SI unit, of energy in 1888. This was because of the invaluable work he did in researching heat and energy. The Bureau International des Poids et Mesures, the governing body for all SI units, finally adopted it in 1948.

The Joule is a 'derived unit', as it is determined by combining two other standard units together - force x distance. This is typically expressed as Newtons x metres. The Joule is often used alongside the calorie as the unit of energy, such as on packets of food.