Motor coil is the time to pay attention, when we turn off the power, pay attention to the coil discharge, which is why, we all know that energy conservation is the energy does not disappear, but from one form to another form. When the electric current through the resistance, the energy becomes the heat, and the energy is distributed around. And when we power when it is connected to the coil, inductance, electric energy is converted into magnetic energy. The magnetic field energy is relatively easy to be automatically converted with electric energy. When we turn off the power, energy storage coil into electricity, to make up for the electric field gradually disappeared. From the external performance, that is, the coil current will slowly down. And that is usually what we say: the inductive load is the continuity of the current. This time, if we are not just the power off, but the inductance of the load end of the circuit is completely open circuit, we will not only see a continuous decline in the current, but also can see the rapid rise of the inductance at both ends. When the voltage is increased to a certain extent, the air can be formed. This principle explains why DC brush motor in reversing when there will be Mars, also explains in the US in the 1970s and 1980s life pull off gates can see sparks jump phenomenon, this is the motor coil should pay attention to, although we do not pay much attention to this, but I really want to pay attention to. Some of the consequences are unimaginable.