Introduction:
Magnets are substances that can attract or repel each other. If tiny molecules in an object can be arranged in the same direction, it will become a magnet. The components are atoms with special structures such as iron, cobalt and nickel, and the atoms themselves have magnetic moments, so the general molecules of these minerals are arranged in disorder. When magnetic fields interact, they can't show magnetism, but under the guidance of external forces (such as magnetic fields), the molecular arrangement directions tend to be consistent, showing magnetism, which is also commonly known as magnets. Iron, cobalt and nickel are the most commonly used magnetic substances. Basically, magnets are divided into permanent magnets and soft iron. Adding strong magnetism to the permanent magnet makes the spin of the magnetic substance arrange in a fixed direction with the angular momentum of the electrons, while adding current to the soft magnet (also a method of adding magnetism) to remove the soft iron, and the soft iron will gradually lose its magnetism. Magnets are not invented by humans, but there are natural magnetite. It should be China who first discovered and used magnets. Therefore, the compass is one of the four great inventions of China people.
Application of electromagnet in daily life;
(1) electromagnetic crane:
Electromagnets are widely used in practice, and the most direct application is electromagnetic cranes. Install the electromagnet on the crane, suck up a large amount of steel after electrifying, cut off the current after moving to another position, and put down the steel. Large electromagnetic cranes can lift several tons of steel at a time.
(2) electromagnetic relay:
Electromagnetic relay is an automatic switch controlled by electromagnet. Using electromagnetic relay can control high voltage and strong current with low voltage and weak current, and realize long-distance operation.
(3) ringtone:
When the circuit is closed, the electromagnet attracts the elastic piece to make the hammer move in the direction of the iron bell, and the hammer hits the iron bell to make a sound. At the same time, the circuit is disconnected, the electromagnet loses its magnetism, and the hammer is bounced back, thus closing the circuit. So repeatedly, the bell keeps ringing.
(4) Electromagnetic concentrator:
Electromagnetic concentrator is made according to the principle that magnets are attractive to iron ore. When the electromagnetic concentrator works, iron ore will fall into box B. In the process of falling, when the ore passes through the electromagnet, non-iron ore can not be attracted by the electromagnet, but directly falls into box A due to the action of gravity. Iron ore can be attracted by electromagnets, adsorbed on the drum and rotated with the drum. When it reaches the top of box B, the electromagnet has little attraction to the ore, so the ore falls into box B due to gravity.
(5) Maglev train:
Maglev train is a high-speed maglev train system with contactless electromagnetic levitation, guidance and drive system. Its speed can reach more than 500 kilometers per hour, making it the fastest ground passenger transport in the world today. It has the advantages of high speed, strong climbing ability, low energy consumption, low noise during operation, safety and comfort, no oil consumption and little pollution. And the overhead way is adopted, which occupies less cultivated land. Maglev train refers to the use of the basic principle of magnetic force to suspend these trains on the guide rail to replace the old steel wheels and track trains. Magnetic levitation technology uses electromagnetic force to lift the whole train car, get rid of annoying friction and unpleasant clang, and realize rapid "flight" without touching the ground and fuel.
(6) Speaker:
A loudspeaker is a device that converts electrical signals into sound signals. It is mainly composed of a fixed permanent magnet, a coil and a cone-shaped paper basin. When sound passes through the coil in the speaker in the form of audio current, the magnetic field generated by the magnet on the speaker will exert force on the coil, and the coil will vibrate with different frequencies due to the change of current intensity, thus driving the paper basin to emit sounds with different frequencies and intensities. The paper basin vibrates through the air, so it produces the sound we hear.
(7) Household appliances:
Such as refrigerators and vacuum cleaners, have electromagnets. Electromagnets are also used in motors, generators and electromagnetic relays. The inlet and outlet valves of the automatic washing machine and the induction flushing valve of the toilet are also controlled by electromagnets.