Amperage

The electric current or short amperage indicates how much electrical charge passes through a defined cross section, based on the amount of time needed for this. The charge transport can be described as a directed movement a plurality of elementary charges, which are generally worn by electrons or ions; see also Electrical power.

The current level is indicated by the symbol ' A, named after the French physicist and mathematician André- Marie Ampère in the International System of Units (SI) in the unit ampere. The symbol is that it comes from " intensity " (referring to the strength of the current). To mark a time dependence using the lower case for the instantaneous value.

Definition

For a time-invariant flow of charge

With the amount of charge which is shifted in time, and the current density passing through a surface element.

The electric current is considered as the transport of elementary particles and thus as quantized size or outside the countability as a continuous and differentiable size; see Electrical charge. Thus applies for a time-varying current

A time- periodically varying amperage (eg AC) has a time constant effective value which is accordingly also characterized by the symbols.

Direction

Since the current is a scalar quantity, set the flow arrows used in many showings are fixed sign. A reversal of direction of the arrow represents a reversal in the sign of their size value for the same amperage.

The technical direction of the current sets with direct current flowing outside a source from the positive to the negative pole, the direction as positive proof. Even with AC a certain direction is useful when flow arrows to indicate the direction of energy flow.

Measurement

A measurement provides a quantitative statement as a multiple of the unit. In addition to the instruments with only one measuring range are available for laboratory, service and field use switchable multimeter with multiple ranges. For industrial applications and for the function of surveillance, there are measuring devices in which the result is not displayed, but remotely transmitted or processed electronically.