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In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. [1] The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point.
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
Or if the current is forced to some value I, then the measured voltage V divided by that current I is also R. Since the plot of I versus V is a straight line, then it is also true that for any set of two different voltages V 1 and V 2 applied across a given device of resistance R , producing currents I 1 = V 1 / R and I 2 = V 2 / R , that the ...
An electric current is a flow of ... a negative value for the current implies the actual direction of current through that circuit element is opposite that of the ...
The average of a symmetric alternating value is zero and it is therefore not useful to characterize it. Thus the easiest way to determine a quantitative measurement size is to use the average rectified value. The average rectified value is mainly used to characterize alternating voltage and current. It can be computed by averaging the absolute ...
The red dot e 1 shows a conduction electron in the sheet right after it has undergone a collision with an atom, and e 2 shows the same electron after it has been accelerated by the magnetic field. On average at e 1 the electron has the same velocity as the sheet (v, black arrow) in the +x direction.
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Any stationary voltage or current waveform can be decomposed into a sum of a DC component and a zero-mean time-varying component; the DC component is defined to be the expected value, or the average value of the voltage or current over all time. Although DC stands for "direct current", DC often refers to "constant polarity".