Magnetic Circuit
The closed path followed by magnetic flux is known as magnetic circuit. A magnetic circuit usually consists of materials having high permeability.
The amount of magnetic coil depends upon current (I) and number of turns (N). If we increase the current or number of turns, the amount of magnetic flux also increases and vice versa. The product of NI is called magnetomotive force (mmf).
Analysis of Magnetic Circuit
l = mean length of the magnetic circuit in meters
a = effective area of the core in m^{2}
μ_{r}_{ }= relative permeability of the core material
N = number of turns
I = current passed through the circuit in ampere
Φ = flux set up in the core in weber
Important Terms of Magnetic Circuit
Flux:- The number of lines of force in a magnetic circuit is called flux. The unit of magnetic flux is the Weber (Wb). It is denoted by Φ.
Magnetomotive force:- It is a force that set up magnetic flux in a magnetic circuit. The unit magnetomotive force is AT.
mmf = NI ampere-turns (AT)
Reluctance:- The opposition that the magnetic circuit offers to magnetic flux is called reluctance. The unit of reluctance is AT/wb. It is denoted by S.
Reluctance depends upon the following factors:-
Permeance: – it is reciprocal of reluctance. The unit of permeance is Wb/AT.
Reluctivity: – It is the specific reluctance.
Analogy of Electric Circuits and Magnetic Circuits
Sr No. |
Electric Circuit |
Magnetic Circuit |
1 |
Volatge(V) |
MMF(AT) |
2 |
Current (I) |
Flux (Φ) |
3 |
Resistance (R) |
Reluctance (S) |
4 |
Resistivity (Rho) |
Reluctivity (1/μ) |
5 |
Current Density (A/m) |
Flux Density (Φ/m) |
Dissimilarities of Electric Circuits and Magnetic Circuits
B-H Curve
The curve drawn between magnetic flux density (B) and magnetizing force (H) is called B-H curve.
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