When did the knowledge of:

 

J = kg * (m/s)²

 

come about exactly?

 

Question has been bugging me off and on.

Electrolysis in early XIX century was used as the primitive ampere meter.

If you put two gold electrodes to water, and attach battery, amount of produced gases is straight depending on current I.

 

You can see electrolysis of water with gold electrodes on video:

https://www.youtube.com/results?search_query=electrolysis+of+water+gold

 

Q=I*t [A*s=C]

 

Power P=U*I [V*A=W]

and

Energy E=U*I*t=U*Q [V*A*s=V*C=J]

 

If voltage will be significant, water will be heated during this experiment. So we can read temperature increase.

 

Joule passed current through resistor placed in water, and heated water, reading temperature difference before and after experiment on thermometer.

Current I, and voltage U, and time can be read from ampere meter, voltage meter, and stopper.

https://en.wikipedia.org/wiki/Joule_heating

Edited August 1, 201510 yr by Sensei

Whilst Joule performed many useful experiments that pushed forward the boundaries of science, he not produce the equation you mention.

 

In fact no one person did it was a collaborative development during the 19th century, stating with Fourier in Mathematics.

 

See the history of dimensional analysis here

 

https://en.wikipedia.org/wiki/Dimensional_analysis