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In special and general relativity, the four-current (technically the four-current density) [1] is the four-dimensional analogue of the current density, with units of charge per unit time per unit area. Also known as vector current, it is used in the geometric context of four-dimensional spacetime, rather than separating time from three ...
The new transformers were 3.4 times more efficient than the open-core bipolar devices of Gaulard and Gibbs. [15] The Ganz factory in 1884 shipped the world's first five high-efficiency AC transformers. [16] This first unit had been manufactured to the following specifications: 1,400 W, 40 Hz, 120:72 V, 11.6:19.4 A, ratio 1.67:1, one-phase ...
A current in a wire or circuit element can flow in either of two directions. When defining a variable to represent the current, the direction representing positive current must be specified, usually by an arrow on the circuit schematic diagram. [12] [13]: 13 This is called the reference direction of the current .
Angle notation can easily describe leading and lagging current: . [1] In this equation, the value of theta is the important factor for leading and lagging current. As mentioned in the introduction above, leading or lagging current represents a time shift between the current and voltage sine curves, which is represented by the angle by which the curve is ahead or behind of where it would be ...
In this case, the voltage refers to the voltage across a biological membrane, a membrane potential, and the current is the flow of charged ions through channels in this membrane. The current is determined by the conductances of these channels. In the case of ionic current across biological membranes, currents are measured from inside to outside.
This way up to 48 white LEDs in series can be powered (for example, 3.1 V/20 mA/20000 mcd). Analyzing the circuit of the lamp shown in the image, at 50 Hz, the 1.2 μF capacitor has a reactance of 2.653 kΩ. By Ohm's law, the current is limited to 240 V/2653 Ω ≈ 90 mA, assuming that voltage and frequency remain constant. The LEDs are ...
Breaking current may be stated in terms of the total current or just in terms of the alternating-current (symmetrical) component. Since the time of opening of a fuse or switch is not coordinated with the reversal of the alternating current, in some circuits the total current may be offset and can be larger than the alternating current component ...
First, three of these terms are associated with sign ambiguities: the line integral ∮ C could go around the loop in either direction (clockwise or counterclockwise); the vector area dS could point in either of the two directions normal to the surface; and I enc is the net current passing through the surface S, meaning the current passing ...