Alternating current: parallel circuits

This chapter discusses the phase relationships between voltage and current for the three basic circuit elements of resistance, inductance, and capacitance. When resistance, inductance, and capacitance are connected in various parallel combinations, problems arising are solved in general in a manner similar to the methods used for parallel resistor circuits but bearing in mind that the branch currents are no longer necessarily in phase. Electric charges flow backwards and forwards round the loop, and there is a constant interchange of energy between the magnetic field of the inductance and the electric field of the capacitance. When it is assumed that the circuit is free of resistance, there is no dissipation of energy and the oscillatory interchange in the closed loop proceeds indefinitely, some resistance is always present so the circulating currents cannot be maintained without some energy being drawn from the supply.