Polarity (physics)

The term polarity describes the addition or arrangement of two poles (opposite extreme points) in space.

This can be, for example:

• Poles of an electrical potential difference ( electrical voltage , for example a battery )
• the alignment of the two areas on a magnet, in the vicinity of which the magnetic field strength is particularly high, see magnetism
• Anode and cathode of a diode and their position during installation
• Connections of an AC voltage source in relation to its phase position (inverted or not inverted)

The polarization indicates the formation of opposite charges in a in this context insulating -body due to an inhomogeneous distribution of charge. The direction of polarization ( transverse waves , antennas , electromagnetic waves , light), on the other hand, only has something to do indirectly with polarity.

Molecules are polar if they have different centers of charge of their positive and negative charges, see polarity (chemistry) .

Further examples

If the two a / b wires of an analog telephone connection are reversed in polarity in b / a , a simple telephone will still work, although DC voltage (60 V) is applied to the telephone connection. The polarity or polarity is - as with AC - consumers the power grid - not matter.

In contrast, the polarity is mandatory or important in the following cases:

• Series connection of transformer windings (alternating voltage in antiphase or in phase)
• Assignment of the three outer conductors for three-phase current (determines the direction of rotation)
• Polarity or polarity of a diode ; see also rectifier , freewheeling diode
• Polarity of an electrolytic capacitor
• Polarity of a battery (motor vehicle, battery-operated devices)

The polarity of a voltage source can be reversed with a double changeover switch or an H-bridge .