Fundamentally, is the difference between the 3, just a capacitive load is a broad dead stop of a metal with a displacement current bubbling out trying to influence nearby metals of lower potential, an inductive load being the cumulative(coils\turns) magnetic fields resisting current flow, & resistive load being a point of high physical resistance (or low conductivity) resulting in massive power released in heat?

What are the functional differences(circuitry) & field differences(Electrical & magnetic)?

How do each of the 3 behave differtly when operating at the high end of their capability spectrum?(50kV(or higher) for capacitor, 10kA(highest I've found possible is 20kA) for inductive & resistive loads)


2 Answers 2


The fundamental difference is in the voltage versus current phase relationship. A purely resistive load has current draw exactly in phase with an AC exciting signal (or power source). A purely capacitive load has current peaks during the fastest rise time, which is current phase lead by ninety degrees. A purely inductive load has current peaks during the fall times of the AC input voltage, i.e. phase lags by ninety degrees.

The physics behind this is that capacitive behavior results from stored electric energy in the form of electric fields, while inductive behavior results from stored electric energy in the form of magnetic fields. Termination resistors for transmission lines are chosen so that the electric and magnetic field energy contributions are equal (result: a transmission line and terminator equal to a resistive load).

Basic physics of electric power delivery is that the Poynting vector (cross product of electric and magnetic field vectors) points at the energy-losing part. The fact of energy delivery REQUIRES magnetic field and electric fields both being nonzero. Power isn't delivered without both types of field being considered.

If the fields are out of phase, that Poynting vector is diminished, but you still have current and voltage (both of which have cost, generate losses); it is most economic to have energy transmission to a 'resistive' load.


A capacitive load is one which upon initial turn-on presents a short circuit to ground, and current flows before the voltage across the element begins to climb. So we say that current leads voltage in a capacitive load.

An inductive load is one which upon initial turn-on presents an open circuit, and the voltage is high before the current begins to flow. So we say that current lags behind voltage in an inductive load.

In a resistive load, there is neither lag nor lead: upon initial turn-on, voltage and current are always strictly proportional to one another.

For very high voltages, a capacitive load leaks current and ionizes the air nearby through a mechanism called corona discharge. If the voltage is high enough, the dielectric between the plates breaks down and becomes conductive, causing the capacitor to melt or explode.

For very high currents, an inductive load heats up and dissipates power. If the current is high enough, the inductor melts and then explodes.

For very high power levels, the resistive load also gets hot and catches fire.


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