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The following is a list of notable unsolved problems grouped into broad areas of physics. [1]Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result.
The electric potential arising from a point charge, Q, at a distance, r, from the location of Q is observed to be =, where ε 0 is the permittivity of vacuum [4], V E is known as the Coulomb potential. Note that, in contrast to the magnitude of an electric field due to a point charge, the electric potential scales respective to the reciprocal ...
The work per unit of charge is defined as the movement of negligible test charge between two points, and is expressed as the difference in electric potential at those points. The work can be done, for example, by generators , ( electrochemical cells ) or thermocouples generating an electromotive force .
Position vectors r and r′ used in the calculation. The starting point is Maxwell's equations in the potential formulation using the Lorenz gauge: =, = where φ(r, t) is the electric potential and A(r, t) is the magnetic vector potential, for an arbitrary source of charge density ρ(r, t) and current density J(r, t), and is the D'Alembert operator. [2]
[Note 1] The original two-variable problem has been reduced to a one-variable problem. For many applications the effective potential can be treated exactly like the potential energy of a one-dimensional system: for instance, an energy diagram using the effective potential determines turning points and locations of stable and unstable equilibria.
The work of forces generated by a potential function is known as potential energy and the forces are said to be conservative. Therefore, work on an object that is merely displaced in a conservative force field , without change in velocity or rotation, is equal to minus the change of potential energy E p of the object, W = − Δ E p ...
Its reduction with increasing frequency, as the ratio of skin depth to the wire's radius falls below about 1, is plotted in the accompanying graph, and accounts for the reduction in the telephone cable inductance with increasing frequency in the table below. The internal component of a round wire's inductance vs. the ratio of skin depth to radius.
The Coulomb potential of electromagnetism is an example of a Yukawa potential with the factor equal to 1, everywhere. This can be interpreted as saying that the photon mass m is equal to 0. The photon is the force-carrier between interacting, charged particles.