Terminology » RF Basics » Electric vs. Magnetic Circuits: Key Differences Explained

Electric vs. Magnetic Circuits: Key Differences Explained

electric circuit magnetic circuit mmf flux reluctance

This article outlines the differences between electric circuits and magnetic circuits, highlighting the analogous properties and distinct behaviors of each.

Electric Circuit vs. Magnetic Circuit

The table below summarizes the key distinctions:

Electric CircuitMagnetic Circuit
What Flows is Current (I)What seems to flow is Magnetic Flux (Φ)
The Cause of Current Flow is EMF (Voltage)The Cause of Flux Flow is MMF (Magnetomotive Force)
Resistance to Current Flow is Resistance (R)Resistance to Flux Flow is Reluctance
Current = EMF / ResistanceFlux = MMF / Reluctance
(i) EMF is expressed in Volts(i) MMF is expressed in Ampere-Turns
(ii) Current is expressed in Amperes(ii) Flux is expressed in Webers
(iii) Current density is expressed in Amp/m²(iii) Flux density is expressed in Wb/m²
Resistance R = 1/σA (σ = Conductivity)Reluctance = 1/μA (μ = Permeability)
Conductance = 1/ResistancePermeance = 1/Reluctance
Conductivity = 1/ResistivityPermeability = 1/Reluctivity
Current actually flowsFlux does not actually flow
Energy is needed as long as current flowsEnergy is needed only to create flux, not maintain it
If temperature is constant, resistance is constant and independent of currentFor a particular temperature, permeability (magnetic conductivity) depends upon the total flux.

In essence, while both circuits involve a driving force and a flow, the nature of what “flows” and the energy requirements differ significantly. Current in an electric circuit represents the movement of electrons, and energy is continuously consumed as long as the current exists. In contrast, magnetic flux is a representation of a magnetic field, not a physical flow of particles, and energy is primarily needed to establish the field.