Comparison between electrical circuit and magnetic circuit
From Amperes law we know that mmf (magneto motive force) around a closed path is equal to the current enclosed by the closed path.
That is integration of H.dl = Ni ………(1)
Where H = magnetic field intensity,
dl = small incremental length,
N = number of conductors and
i = current flowing in each conductors.
Now if H is constant then from equation (1)
Integration of H.dl = Ni
→ (H) integration of dl = Ni
→ H . l = Ni
therefore H = Ni/l ………(2)
Now because flux ф = B.A = μH.A (because B = μH) …………(3)
Where B = magnetic flux density, H = magnetic field intensity, μ = permeability of medium and A = area.
Now from equation (2) and equation (3)
Ф = μNil /A
→ Ф = Ni / ( l / μA) ………………(4)
Similarities between magnetic circuit and electric circuit
- Magnetic circuit follows equation (4) that is Ni = (Ф) ( l / μA) or m.m.f(magneto motive force) = (Flux) (reluctance).
Electric circuit follows ohm’s law that is E = I.R or e.m.f(electro motive force) = (current) (Resistance)
- From above point m.m.f in magnetic circuit is like as e.m.f in electrical circuit.
- Flux in magnetic circuit is similar as current in electrical circuit.
- Reluctance in magnetic circuit, S = ( l / μA) is similar to resistance R = (ρl/A) in electric circuit.
- Permeance (= 1/reluctance) in magnetic circuit is equivalent to conductance (=1/resistance) in electric circuit.
Differences between magnetic circuit and electric circuit
- In magnetic circuit flux establishes but not flow like as current in magnetic circuit.
- In magnetic circuit energy needed only to establish the flux but no consistent energy need to maintain it whereas in electric circuit continuous energy needed to flow of current.
- Resistance of an electric circuit is constant (for same temperature) and is independent of current but reluctance of magnetic circuit is not constant because it depends on μ (=B/H) which is not constant and depends on B/H.