Inductors mainly play the role of filtering, oscillation, delay, notch, etc. in the circuit, as well as screening signals, filtering noise, stabilizing current and suppressing electromagnetic wave interference.

The structure of inductor is similar to that of transformer, but there is only one winding, which is generally composed of skeleton, winding, shielding cover, packaging material, magnetic core or iron core, etc. If the inductor is in the state of no current passing, it will try to prevent the current from flowing through it when the circuit is connected; If the inductor is in a state of current flow, it will try to maintain the current when the circuit is disconnected.

The inductor is composed of coils surrounded by magnetic materials. When the current passes through the inductor, it will create a magnetic field, which does not like to be changed. Therefore, an inductor is an element that will prevent the current flowing through it from changing; If the current flowing through the inductor is constant, the inductor will feel very comfortable and will not create additional force on the charged particles flowing through it. In this case, the inductor behaves like a normal wire.

However, if we try to block the current flowing through the inductor, the inductor will create a force to maintain the current flowing through the inductor. If an inductor is connected end to end, and the circuit has no other resistance, in theory, the current can flow forever without decay.

However, unless we use superconductors, any wire itself has resistance, which will cause the final current to decay to zero. The greater the resistance in the circuit, the faster the current decay; However, the larger the inductance of the inductor, the slower the current will decay. Once the current decays to zero, the inductor will try to maintain the current status of zero; This is because the inductor always tries to stop the current flowing through it from changing.

Therefore, when we connect the inductor to a circuit, at first, the inductor will generate a force, which will prevent the current from increasing.