How do magnetic and electric fields differ?

Electric and magnetic fields

Electric fields - what is an electric field?

When two oppositely polarized, voltage-carrying conductors face each other, an electric field is created between them. Electric fields are present wherever there is electrical voltage. Current flows when the electric field strength or the density of the field lines is large enough. As a rule, however, only when the space between the poles becomes conductive. If the field strength is large enough, a spark discharge occurs. Something like this happens, for example, in a thunderstorm when there is lightning. This effect is also used, for example, in the spark plug in the car.

However, there are different electric fields. With a direct voltage, there is a static electrical direct field. With an alternating voltage, there is a dynamic alternating electrical field. A distinction is made between low and high frequency fields. The alternating voltage from the socket is a low-frequency alternating field (with 50 Hz).
The electric field strength is given in volts per meter (V / m).

Basically, we are constantly exposed to electrical fields. Electric fields try to move charges that are expressed in a current flow. The human body is to be understood as an electrical conductor, even if it is not a particularly good conductor. Charge shifts can occur in the human body under the influence of electrical fields. But they are only noticeable at very high field strengths. You then feel a slight tingling sensation. However, we can only be exposed to such high field strengths in a substation. They do not occur in the free environment. Not even artificially created.
Most of the sensations we attribute to electric fields are imaginary. It is much more likely to be magnetic fields, which only arise when there is a flow of electricity. That is why it applies to electric fields that they are completely harmless without current flow. There is no danger from a socket or electrical line that does not have any current flowing through it.

Magnetic fields - what is a magnetic field?

The flow of electricity and electromagnetism are inextricably linked. The connection between current and magnetism is expressed in the term "electromagnetic". For example with electromagnetic compatibility (EMC). The conductor only surrounds itself with a magnetic field where a current flows. The field lines are arranged in a circle around the conductor.
However, there are different magnetic fields. With direct current, a static magnetic direct field is created. With alternating current, a dynamic alternating magnetic field is created. In the case of alternating fields, a distinction is made between low-frequency and high-frequency fields. Devices that are connected to the low-frequency alternating voltage can emit high-frequency alternating fields. For example, electric motors and fluorescent lamps.
The field strength of magnetic fields is given by the magnetic flux density in Tesla (T). In practice, the units µT and mT are used. The Gauss (G) unit for magnetic flux density has established itself internationally. 1 G corresponds to 10-4 T. So 1 mT equals 10 G. Or 1 µT equals 10 mG.

Personal protection defines a limit value of 1 mT for a maximum of 6 hours per day as harmless. Large-scale household appliances (vacuum cleaners, drills, hair dryers) can generate magnetic fields with several mT. As a rule, we are only exposed to these influences for a short time. The risk is correspondingly low. A magnetic flux density of 0.2 to 0.5 mT occurs in the tube television. But even at a distance of 50 cm, the magnetic flux density is only about 1% of that. If you compare these parameters with each other, there is no harm to people by watching TV directly in front of the TV.

Electrosmog

In and of themselves, magnetic fields are not harmful. But if you reverse the electromagnetic effect, then it can have negative effects on the human organism. When the magnetic flux changes around an electrical conductor, a voltage is induced that can cause a current to flow. Nerve pathways act like electrical conductors that can be influenced by external magnetic fields. In this way, stimuli can be captured that can unbalance the human organism. In practice, extreme tissue heating or cardiac arrhythmias are known.
If you look for potential hazards, you quickly come across high-voltage lines that are laid in the air but also in the ground. Because of the high voltage, very intense electric fields also occur there. Due to the high currents that flow on these lines, magnetic fields with great strength are also generated. Magnetic flux densities of 0.2 to 0.3 µT occur at a distance of 50 to 100 meters from high-voltage lines. But these values ​​are already clearly exceeded by other parties. For example with household appliances.
The problem with electrosmog is the lack of objectivity with which it is discussed. This is hardly surprising, as there are extremely controversial views, especially among experts. Basically, one should take into account that health impairments usually have more than just one trigger.

Measurement of electric and magnetic fields

An electric field is measured with an electric field meter. An electric field meter, also known as an electric field meter, rotary voltmeter or field mill, is a device for measuring the strength of the electric field.

A magnetic field is measured with a magnetic field meter. This is a device for measuring the magnetic field strength. In contrast to electric fields, magnetic fields can be measured very precisely because they penetrate most materials and are hardly influenced by the environment.

Various methods or sensor types can be used to measure magnetic fields. The use of components and sensors that reduce their electrical resistance is widespread
Change magnetic field influence.

The magnetic field strength is given in A / m (amperes per meter). In practice, however, the magnetic flux density is measured in T (Tesla). Field strength and flux density are linked to one another via the magnetic field constant and can be converted into one another. Because Tesla is a very large unit, measurements of everyday exposure are usually given in the unit microtesla (µT).

Most of the time, the measuring units of both measuring units are located in one measuring device. So you can measure electric and magnetic fields with one device.
The measuring devices are usually built for a specific frequency range. A measurement error can amount to several percent. This can be due to the tolerance of the measuring device, but also to a human error. In principle, all measurement results should only be viewed with reservations if measurements with clear, reproducible measurement conditions cannot be guaranteed.

Other related topics:

Electronics simple and easy to understand

Electronics primer

The electronics primer is a book about the basics of electronics, components, circuit technology and digital technology.

I want that!

Experience electronics with the "Starter Edition" electronics set

Perfect for beginners and newcomers

  • Entry into electronics without prior knowledge
  • Quick understanding of components and circuit symbols
  • Experiment without a soldering iron: just insert components

More informationOrder the electronics set now