Editing Conjugate variables (section)

===Derivatives of action===
In [[classical physics]], the derivatives of [[action (physics)|action]] are conjugate variables to the quantity with respect to which one is differentiating. In quantum mechanics, these same pairs of variables are related by the Heisenberg [[uncertainty principle]].
* The ''[[energy]]'' of a particle at a certain [[event (relativity)|event]] is the negative of the derivative of the action along a trajectory of that particle ending at that event with respect to the ''[[time]]'' of the event.
* The ''[[linear momentum]]'' of a particle is the derivative of its action with respect to its ''[[position (vector)|position]]''.
* The ''[[angular momentum]]'' of a particle is the derivative of its action with respect to its ''[[orientation (geometry)|orientation]]'' (angular position).
* The ''[[Relativistic angular momentum#Dynamic mass moment|mass-moment]]'' (<math>\mathbf{N}=t\mathbf{p}-E\mathbf{r}</math>) of a particle is the negative of the derivative of its action with respect to its ''[[rapidity]]''.
* The ''[[electric potential]]'' (φ, [[voltage]]) and ''[[electric charge]]'' in a [[quantum LC circuit]].<ref>{{Cite journal |last=Vool |first=Uri |last2=Devoret |first2=Michel |date=2017 |title=Introduction to quantum electromagnetic circuits |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/cta.2359 |journal=International Journal of Circuit Theory and Applications |language=en |volume=45 |issue=7 |pages=897–934 |doi=10.1002/cta.2359 |issn=1097-007X|arxiv=1610.03438 }}</ref>
* The ''[[Magnetic vector potential|magnetic potential]]'' ('''A''') at an event is the derivative of the action of the electromagnetic field with respect to the density of (free) ''[[electric current]]'' at that event. {{citation needed|date=April 2013}}
* The ''[[electric field]]'' ('''E''') at an event is the derivative of the action of the electromagnetic field with respect to the ''electric [[polarization density]]'' at that event. {{citation needed|date=April 2013}}
* The ''[[magnetic field|magnetic induction]]'' ('''B''') at an event is the derivative of the action of the electromagnetic field with respect to the ''[[magnetization]]'' at that event. {{citation needed|date=April 2013}}
* The Newtonian ''[[gravitational potential]]'' at an event is the negative of the derivative of the action of the Newtonian gravitation field with respect to the ''[[mass density]]'' at that event. {{citation needed|date=April 2013}}