By hvhipot 
If a capacitor and an inductor are connected in series, the circuit will display zero reactance for a sinusoidal signal of a certain frequency. This effect is called resonance of an oscillating circuit, and the circuit itself from capacitors and inductors is called a sequential oscillating circuit, and the frequency exhibited by this effect is the resonance frequency.
Although both inductors and capacitors have a certain reactance, they do not exhibit reactance together. The reason is simple. Capacitors and coils accumulate and release energy, but they function in different ways. At the moment when the coil accumulates energy, the capacitor will release energy, and vice versa. Of cHV Hipot Electric Co., Ltd.se, this effect is only manifested in steady state with a sine signal of a certain frequency. If the frequency is very different from the resonant frequency, the circuit will lose its excellent quality and behave as a coil and capacitor. If the serial oscillation circuit is not powered on and a sine signal of resonant frequency has been applied to it, the resistance will gradually decrease as the circuit enters a stable working state.
If a sine current of resonant frequency passes through a series resonant circuit, the voltage drop across the circuit will be zero. But the voltage drop across the capacitor will occur separately, and the inductance will occur separately. Just these pressures cancel each other out at every moment. The voltage on capacitors and coils may be very high. One of the common errors in designing a series resonant circuit is the inaccurate estimation of the voltage across the capacitor. The voltage can be several times, tens of times, or hundreds of times the power supply voltage. Based on this influence, a scheme for boost converters has been developed. It should also be noted that the current flowing through the series circuit will not saturate the core of the inductor.
In a circuit, if it is necessary to skip a signal of a certain frequency and filter out all other signals, a sequential oscillation circuit is used. The vibration circuit is very small and designed to operate with small currents and voltages, for example, in the input and internal circuits of a radio receiver. However, there are power amplifiers designed specifically for high current and high voltage in wireless transmitters, power resonant filters, and other applications.