Load resistance

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The load resistance is the electrical resistance with which an electrical energy or signal source is loaded. If this has the behavior of a voltage source , the load resistance determines the electrical current and the electrical power that are delivered by the source. In the general sense, the load resistance can also be an alternating current resistance (an impedance ), which is composed of an effective resistance and a reactance .

In three-phase systems , the term symmetrical load is used when the impedance of the consumer is the same in all phases. The impedances unequal, then provides the an unbalanced load. In the electric power networks for the term is unbalanced load used.

The load resistance of the source is at the same time the internal resistance of an electrical consumer or the input resistance of another electrical device.

If the load resistance is infinite, this case is called open circuit , if the load resistance is zero, there is a short circuit .

A power adjustment is sometimes aimed for in signal transmission . The aim of this is to pass on the power as completely as possible to sources that can only generate low electrical power. For this purpose, the load resistance must be selected as large as the internal resistance of the signal source. Reflections on transmission lines can be avoided if the characteristic impedance of the line is also equal to the load resistance.

When transmitting energy, the aim is usually to adjust the voltage with the lowest possible energy loss, for which the load resistance must be significantly greater than the internal resistance of the energy source.

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