1. The relay is composed of four parts, namely coil and magnetic circuit reaction spring and contact. The function of the coil is to generate electromagnetic attraction after electrification, drive the cohesive absorption of the magnetic circuit, and make the contacts displace.

2. Magnetic circuit The task of the magnetic core iron choke coil and electric drill is to create a magnetic circuit for the magnetic circuit generated by the coil. In the magnetic circuit, the most important thing is the magnetic circuit air gap, that is, the gap between the electric drill and the iron core. When the coil is not energized, the air gap is at the maximum value, and the contacts are in the initial state; after the coil is energized, the air gap is zero, and the contacts become dynamic. After the coil is de-energized and released, the normally closed and normally open contacts are reset to their initial states.
3. There are three types of relays, namely voltage relays, current relays and intermediate relays. The voltage relay has a large number of coils, thin wire diameter, and the coils are parallel to the load. The voltage relay is our common type of main relay. The number of coils of the current relay is small, the wire diameter is thick, the coil is connected in series with the load, and the working current is the load current. The 24V relay can only be used in the working system of 24V power supply, and it can also be used alone with the 12V relay. There is an internal structure diagram on the side of the relay, which is mainly used to drive external high-power loads, and is usually used for low-side drive output functions. Its working principle is that pins 85 and 86 supply power to the internal coil through the voltage difference, and the coil absorbs the internal switch through electromagnetic induction, connects pins 30 and 87, and drives an external high-power load to work normally.