Often choose to have a high electrical conductivity and magnetic permeability of the conductor as a shielding material. This is because highly conductive materials will generate large induced currents under the action of electromagnetic waves. These currents in accordance with corrugated law will weaken the penetration of electromagnetic waves. The denser the metal mesh used, or even the use of a whole metal shell, the better the shielding effect, but the more material it costs. Highly permeable materials can guide more magnetic lines of force through these materials, while reducing the number of magnetic lines of force in the shielded area. Shields are usually grounded to avoid being affected by accumulated charges.
Electromagnetic waves penetrating toward a large piece of metal will continue to attenuate until the attenuation is zero. The degree of attenuation increases with the electrical and magnetic permeability of the material and the frequency of the electromagnetic wave. Shielding requirements are often higher when the use of multi-layer shielding. For example, sometimes using cast iron, PoMo alloy, electrolytic copper three materials made of multi-layer shielding to meet the electrical conductivity, magnetic conductivity and other requirements.
But the realization of the complete shielding is very difficult to do, because the shielded area and the rest of the region often still need to have a circuit connection between the lead and the lead, lead and the shell of the insulation gap always exists between the electromagnetic waves still provide access. Even for a completely closed metal shell, the internal magnetic flux density is theoretically not zero under the action of external electromagnetic fields of very low frequency.
Electromagnetic radiation is colorless, tasteless and invisible, and can penetrate a wide range of substances, including the human body. A variety of household appliances, electronic equipment, office automation equipment, mobile communications equipment and other electrical devices as long as the operation of the use of state, it will be around the existence of electromagnetic radiation. According to experts, high electromagnetic radiation environment may have the following effects on human health:
. The impact on the cardiovascular system, manifested as palpitations, insomnia, some women menstrual disorders, bradycardia, decreased cardiac blood flow, sinus arrhythmia, leukopenia, decreased immune function.
. The effect on the visual system, manifested in decreased vision, causing cataracts, etc.
. The effect on the reproductive system, manifested in the occurrence of spontaneous abortion in pregnant women and fetal deformities, etc.
. Prolonged exposure to high electromagnetic radiation will change the blood, lymph fluid and cell protoplasm; affect the circulatory system, immunity, reproduction and metabolic functions of the human body, and in serious cases induce cancer and accelerate the proliferation of cancer cells in the human body.
. Patients with pacemakers are exposed to high electromagnetic radiation, which can affect the normal use of pacemakers.
If you have been involved in an environment with excessive doses of electromagnetic radiation for a long time, you should pay attention to the following self-protection measures:
People who live and work near high-voltage power lines, substations, radio stations, television stations, radar stations, and electromagnetic wave transmitting towers, patients with pacemakers, people who frequently use electronic instruments, medical equipment, and office automation equipment, and people who live in the environment of modern electrical appliances and automation, especially those who live in a modern electrical appliances and automation environment, should be careful to protect themselves. Automation of the environment of the crowd, especially the weaker resistance of pregnant women, children, the elderly and the sick, the conditions should be equipped with shielding for electromagnetic radiation protective clothing, electromagnetic radiation will maximize the blocking of the body outside.
Television, computers and other electrical equipment with a display screen can be installed electromagnetic radiation protection screen, the user can also wear anti-radiation glasses to prevent the screen radiates electromagnetic waves directly on the human body.
Mobile phones are connected to the moment of the release of electromagnetic radiation is the largest, so it is best to ring the phone after a second or two seconds or two phone ringing in the middle of the phone to answer the phone.
The radiation generated by the screen of the TV, computer and other electrical appliances will lead to dry and dehydrated skin, accelerate skin aging, and even lead to serious skin cancer, so you should wash your face in a timely manner after using the above appliances.
More carrots, bean sprouts, tomatoes, greens, kelp, cabbage, lean meat, animal liver and other foods rich in vitamins A, C and protein, in order to regulate the body's electromagnetic field disorders, and strengthen the body's ability to resist electromagnetic radiation.