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A flow of positive charges gives the same electric current, and has the same effect in a circuit, as an equal flow of negative charges in the opposite direction. Since current can be the flow of either positive or negative charges, or both, a convention is needed for the direction of current that is independent of the type of charge carriers ...
Illustration of the "reference directions" of the current (), voltage (), and power () variables used in the passive sign convention.If positive current is defined as flowing into the device terminal which is defined to be positive voltage, then positive power (big arrow) given by the equation = represents electric power flowing into the device, and negative power represents power flowing out.
When it is operating in the second or fourth quadrant, current is forced to flow through the device from the negative to the positive voltage terminal, against the opposing force of the electric field, so the electric charges are gaining potential energy. Thus the device is converting some other form of energy into electric energy.
If electric current is forced to flow through the device in the direction from the lower electric potential to the higher, so positive charges move from the negative to the positive terminal, work will be done on the charges, and energy is being converted to electric potential energy from some other type of energy, such as mechanical energy or ...
Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current. [1]
Field lines of an electric dipole.Field lines go from positive charge (source) to the negative charge (sink). In electrodynamics, the current density behaves similar to hydrodynamics as it also follows a continuity equation due to the charge conservation:
In n-type semiconductors, electrons in the conduction band move through the crystal, resulting in an electric current. In some conductors, such as ionic solutions and plasmas, positive and negative charge carriers coexist, so in these cases an electric current consists of the two types of carrier moving in opposite directions.
By historical convention, a positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current. The motion of negatively charged electrons around an electric circuit, one ...