# laws of physics

** ** ** ** ** LAWS OF PHYSICS**

** ** **The basic laws of physics fall into two categories: classical physics that deals with the observable world (classical mechanics), and atomic physics that deals with the interactions between elementary and sub atomic particles (quantum mechanics). The basic laws of both are listed here in alphabetical order. Some laws apply only to one or the other category; some belong to both. A few of the laws listed may have little impact on petrophysics and some may have been left off the list for any number of reasons.**

** The line integral of the magnetic flux around a closed curve is proportional to the algebraic sum of electric currents flowing through that closed curve; or, in differential form** **curl B = J.**

** This was later** ** modified to add a second term when it was incorporated into Maxwell’s equations.**

** A body that is submerged in a fluid is buoyed up by a force equal in magnitude to the weight of the fluid that is displaced, and directed upward along a line through the center of gravity of the displaced fluid. **

** Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules. It is, in fact, only true for ideal gases.**

**Centrifugal Pseudoforce**** ** **A** ** pseudoforce on an object when it is moving in uniform circular motion. The force is directed outward from the center of motion.**

**There are several other laws that deal with particle physics, such as conservation of baryon number, of strangeness, etc., which are conserved in some fundamental interactions (such as the electromagnetic interaction) but not others (such as the weak interaction). **

** Coriolis Pseudoforce (1835)**** ** **A** ** pseudoforce which arises because of motion relative to a frame of reference which is itself rotating relative to a second, inertial frame. The magnitude of the Coriolis force is dependent on the speed of the object relative to the noninertial frame, and the direction of the force is orthogonal to the object’s velocity.**

**Faraday’s Laws of electrolysis** * Faraday’s first law of electrolysis***The amount of chemical change during electrolysis is proportional to the charge passed.** * Faraday’s second law of electrolysis*** ** **The charge Q required to deposit or liberate a mass m is proportional to the charge z of the ion, the mass, and inversely proportional to the relative ionic mass M; mathematically Q = F m z / M,**

* Faraday’s third law of electromagnetic induction*** ** **The sense of the induced electromotive force depends on the direction of the rate of the change of the field.**

**Lambert’s Laws** *Lambert’s first law***The illuminance on a surface illuminated by light falling on it perpendicularly from a point source is proportional to the inverse square of the distance between the surface and the source.** *Lambert’s second law***If the rays meet the surface at an angle, then the illuminance is proportional to the cosine of the angle with the normal. ** *Lambert’s third law***The luminous intensity of light decreases exponentially with distance as it travels through an absorbing medium.**

**Maxwell’s Equations (1864)**** ** *Gauss’ law*** ** **The electric flux through a closed surface is proportional to the algebraic sum of electric charges contained within that closed surface; in differential form** **div E = rho, **

**where**

*rho*is the charge density.

*Gauss’ law for magnetic fields***The magnetic flux through a closed surface is zero; no magnetic charges exist. In differential form**

**div**

**B****= 0.**

*Faraday’s law***The line integral of the electric field around a closed curve is proportional to the instantaneous time rate of change of the magnetic flux through a surface bounded by that closed curve; in differential form**

**curl**

*E*= -d*B*/d*t*,.**.**

*Ampere’s law, modified form*

**The line integral of the magnetic field around a closed curve is proportional to the sum of two terms: first, the algebraic sum of electric currents flowing through that closed curve; and second, the instantaneous time rate of change of the electric flux through a surface bounded by that closed curve; in differential form**

**curl**

*H*=*J*+ d*D*/d*t*,**.**

**In addition to describing electromagnetism, his equations also predict that waves can propagate through the electromagnetic field, and would always propagate at the the speed of light in vacuum.**