What is a magnetic circuit? To better understand magnetic circuits, a basic understanding of the physical qualities of magnetic circuits will be necessary.

EO 1.8EXPLAIN the physical qualities of a simple magnetic circuit, including relationships of qualities and units of measurements.

EO 1.9Given the physical qualities of a simple magnetic circuit, CALCULATE the unknown values.

EO 1.10 DESCRIBE the shape and components of a BH magnetization curve.

EO 1.11 EXPLAIN the cause of hysteresis losses.

EO 1.12 Given Faraday's Law of induced voltage:

a. DESCRIBE how varying parameters affect induced voltage.

b. CALCULATE voltage induced in a conductor moving through a magnetic field.

EO 1.13 STATE Lenz's Law of induction.

Magnetic Circuits

A magnetic circuit can be compared with an electric current in which EMF, or voltage, produces a current flow. The ampere-turns (NI), or the magnetomotive force (F_m or mmf), will produce a magnetic flux (Figure 26). The mmf can be compared with EMF, and the flux () can be compared to current. Equation (1-16) is the mathematical representation of magnetomotive force derived using Ohm's Law, .

where

Figure 26 Magnetic Current with Closed Iron Path

Equation (1-17) is the mathematical representation for reluctance.

where

Example: A coil has an mmf of 600 At, and a reluctance of 3 x 10⁶ At/Wb. Find the total flux .

Solution: