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In electromagnetism and electronics, electromotive force (also electromotance, abbreviated emf, [1] [2] denoted ) is an energy transfer to an electric circuit per unit of electric charge, measured in volts. Devices called electrical transducers provide an emf [3] by converting other forms of energy into electrical energy. [3]
The surface is the only location where a net electric charge can exist. [4]: p.754 This establishes the principle that electrostatic charges on conductive objects reside on the surface of the object. [3] [7] External electric fields induce surface charges on metal objects that exactly cancel the field within. [3]
Electrical energy is energy related to forces on electrically charged particles and the movement of those particles (often electrons in wires, but not always). This energy is supplied by the combination of current and electric potential (often referred to as voltage because electric potential is measured in volts) that is delivered by a circuit (e.g., provided by an electric power utility).
Electric charge is a conserved property: the net charge of an isolated system, the quantity of positive charge minus the amount of negative charge, cannot change. Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms ...
If a cloth rubs against an object, the object will display an effect called friction electricity. The object becomes charged due to the rubbing process, and now possesses an static electrical charge, hence it is also called static electricity. There are two main types of electrical charge: positive and negative.
Part of the energy needed for this deformation is recovered (elastic deformation), some is not and goes into heating the tires. The energy which is not recovered contributes to the back force, a process called rolling friction. Similar to rolling friction there are energy terms in charge transfer, which contribute to friction.
The force acting on a point charge due to a system of point charges is simply the vector addition of the individual forces acting alone on that point charge due to each one of the charges. The resulting force vector is parallel to the electric field vector at that point, with that point charge removed.
For example, the efficiency of nuclear reactors, where the kinetic energy of the nuclei is first converted to thermal energy and then to electrical energy, lies at around 35%. [ 5 ] [ 6 ] By direct conversion of kinetic energy to electric energy, effected by eliminating the intermediate thermal energy transformation, the efficiency of the ...