The series resonance of inductive and capacitive resistors can result in a smaller phase shift between current and voltage in an AC circuit, which is smaller than when they are separately included in the circuit. In other words, due to the simultaneous action of these two reactors with different properties in the circuit, phase shift compensation occurs.
When the inductive resistance is equal to the capacitive resistance of the circuit, that is, when XL=XC or the same, and when L=1, complete compensation will occur, that is, completely eliminating the phase shift between current and voltage in this circuit.
In this case, the circuit will behave as a pure active resistor, as if there were no coils or capacitors present. The value of this resistor is determined by the sum of the effective resistances of the coils and connecting wires. In this case, the effective value of the current in the circuit will be the largest and determined by the formula I=U/R of Ohm's Law.
At the same time, the applied voltage on coil UL=IXL and capacitor Uc=IXX will be equal and should be as large as possible. In the case where the active resistance of the circuit is small, these voltages may exceed several times the total voltage U on the circuit terminals, and this interesting phenomenon is called series resonance in electrical engineering.
Voltage current and power diagram during series resonance
It should be kept in mind that resistors XL and XC are variables that depend on the frequency of the current, and it is worth at least slightly changing their frequency. For example, as XL=XL increases, XC==1/XC decreases and increases. Therefore, in the circuit, the resonance of the voltage is immediately destroyed, and together with the active resistor, reactance appears in the circuit. If the size of the inductance or capacitance of the circuit is changed, the same situation will occur.
Through series resonance, the power of the current source will only be used to overcome the active resistance of the circuit, that is, to heat the conductor. In fact, in a circuit with an inductor, there is energy resonance, that is, the periodic transition of energy from the generator to the magnetic field of the coil. In a circuit with a capacitor, the same thing happens. However, due to the energy of the capacitor electric field, during the series resonance period (XL=XC) in a circuit with a capacitor and an inductor, the energy distributed by the circuit is periodically transferred from the coil to the capacitor, and vice versa. Only the energy consumption required to overcome the active resistance of the circuit falls on the current source. Therefore, in the absence of a generator, energy is exchanged between the capacitor and the coil.