The basic laws of the magnetic circuit

1. Ampere's Loop Law

For any closed loop,
$${\oint }_{L}H\cdot dl=\sum i\; is$$
special, for the magnetic field intensity is equal everywhere, and the total current enclosed by the closed loop is provided by the N-turn coil with current i, then
$$Hl=Ni$$

2. Ohm's law of the magnetic circuit

$$F=\Phi R_m=\frac{F}{A}$$

$N$ : The number of turns of the coil on the iron core.
$i$ : The current passing through the coil.
$A$ : The cross-sectional area of ​​the core.
$l$ : The average length of the magnetic circuit.
$\mu$ : The magnetic permeability of the material.

3. Kirchhoff's Law of Magnetic Circuits

(1) The first law

$$\sum Phi=0$$

(2) The second law

$$Ni=\sum _{k=1}^n{H}_k{l}_k$$
The total magnetomotive force along any closed magnetic circuit is always equal to the algebraic sum of the magnetic potential drop of each magnetic circuit

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