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Electricity concerns phenomena associated with electric charge, including electric fields and electric currents.

A mathematician associated with Green functions and Green's identities.

James Prescott Joule was an English physicist whose private experiments connected electricity, heat and mechanical work. His family ran a brewery in Salford; he developed an experimental laboratory while working in the family business.^[ref] The Royal Society's archive identifies his occupation as physicist and records his life as 1818–1889.^[ref]

His electrical heating experiments placed metal coils in water and measured the temperature change. Later, he used the brewery cellar to reduce ambient temperature fluctuations during friction experiments and took particular care over thermometer calibration.^[ref] These practical choices address a central difficulty of calorimetry: a small temperature rise can reflect both the intended input of energy and unwanted heat transfer to the surroundings. A quiet baseline and a known heat capacity are part of the measurement, not decoration around the formula.

The contrast between Joule heating and Joule's paddle-wheel experiment makes the connection especially clear. One supplies electrical work; the other supplies mechanical work. In each case, calorimetry tracks the resulting change of internal energy. Comparing quantitatively controlled inputs with thermal changes gives an experimental test of conservation of energy, rather than merely showing that stirring or an electric current can warm water. The paddle-wheel account describes the descending weights, vanes, thermal controls and corrections needed for that comparison.

Joule's free-expansion experiment asks a different question: how does a gas's temperature change during expansion without external work? The Joule-Thomson effect instead concerns flow through a restriction and a balance involving enthalpy. Keeping the two experiments distinct prevents a shared historical name from hiding different system boundaries and different conserved quantities.

Michael Faraday connected chemistry with quantitative electricity through electrolysis. His experimental treatment related the amount of material transformed at an electrode to the electric charge passed through the apparatus, the basis of Faraday's laws of electrolysis.

His candle lectures made a different connection between apparatus and explanation: the wick supplies melted fuel through capillary action, while the flame's products reveal the chemical transformations involved in combustion.^[ref]

A chemist whose route into experimental research began with a bookbinding apprenticeship (1805–1812). He became a laboratory assistant at the Royal Institution in 1813, its laboratory director in 1825, and Fullerian Professor of chemistry from 1833 to 1867.^[ref]

For direct conversion, descending masses can drive paddles in an insulated vessel of water. Measure the lost gravitational potential energy and the temperature rise, including the vessel's heat capacity and corrections for unwanted heat transfer. Repeated reversal of the paddles and fixed baffles inhibit simple bulk co-rotation, directing more of the input towards dissipative fluid motion. Joule's paddle-wheel experiment tests a quantitative mechanical-to-thermal balance, rather than merely observing that stirring can warm water.^[ref]

For conversion through electricity, mechanical work drives a generator, whose electric current passes through a resistor in a calorimeter. The measured electrical input is $\int VIdt$, or $I^{2}Rt$ for constant electric current and electrical resistance. Joule heating increases the internal energy of the resistor and surrounding water. Compare the generator's mechanical input with the total thermal gains, including generator and circuit losses if the system boundary contains them. A battery alone demonstrates electrical-to-thermal conversion; without accounting for a mechanically driven source it does not establish the requested mechanical intermediate chain.

Using the given value relative to water, the copper requiresWith the modern thermochemical calorie, $1\mathrm{cal}=4.184\mathrm{J}$, so the ideal required work isEquivalently it is about $203\mathrm{kgf}\mathrm{m}$ using standard gravity. A nineteenth-century numerical equivalent of heat could give a slightly different rounded result. The stipulated constant specific heat capacity is used here; an unprovided vessel heat capacity and environmental losses would add to the required input.