# What is field

The term plays a role in physics field a central role. A field consists of a space, which can be empty or filled with material, and measurable physical properties that can be assigned to each point in space. The physical quantities can also be multi-component, as in the case of speed. These physical quantities are called field quantities.

### Examples

The term field is used in all branches of physics. examples are

### Motivation of the term

The motivation for introducing the field term lies

1. on the one hand in the simpler description of physical processes in many-body systems. Instead of having to specify all the locations and velocities of the individual particles, the field description enables an elegant method to deal with the temperature and density of a gas or a liquid.
2. on the other hand, in the consideration of the proximity effect, which must be taken into account because of the finite transmission speed of physical events and interactions. The field then consists of physical quantities that cannot be further reduced, such as in the electromagnetic field and in the gravitational field.

### Division of the fields

Another division of fields is their mathematical nature:

• Scalar fields have scalars as field quantities, such as mass density and temperature. An important scalar field is the potential
• Vector fields have vectors as field quantities, such as the electric field strength and the force
• Tensor fields have tensors as field variables, such as elastic tension
• Spinor fields have spinors as field variables, such as the current density in a relativistic field description (Dirac field); fields with spinors of higher order can also be described
• static fields have field sizes that are independent of time
• stationary fields have field sizes that describe a stationary flow of a liquid
• Quasi-stationary fields have field sizes whose change over time is negligible.

### application

Vector fields are most widespread in the practical environment. They can be described particularly clearly with the help of field lines, the tangents of which represent the direction of the field sizes (vectors) at each point in space. The field strength, i.e. the amounts of the field vectors in the spatial points, is represented by the density of the field lines. Such field lines can be clarified in experiments, think of the magnetic field that can be represented by means of iron filings.

Field lines can start from certain points in space (the sources) and disappear at other points (the sinks). Such fields are called spring fields. An example of this is the electrostatic field of a positive and negative electrical charge.

Field lines of other fields can only appear closed in themselves. One then speaks of a vortex field. An example of this is the magnetic field.