Figure 1
When an alternating current is passed through a coil, a changing magnetic field is produced. This magnetic field is proportional to the number of turns of the coil. For an infinite solenoid the magnetic field B is given by: đ??ľ=
đ?œ‡đ?‘œ đ?‘ đ??ź â„“
(1)
Where: Îźo = The permeability of free space (the magnetic constant) N = The number of turns of the wound coil I = The current through the solenoid â„“ = The length of the solenoid If we have two coils with different numbers of turns, N1 and N2, we can pass a current through one coil and use the resulting fluctuating magnetic field to induce an electromotive force in the second coil by placing it in the vicinity of this magnetic field. Using Faraday’s Law the resulting electromotive force is equal to: đ?œ€ = −đ?‘
Where: N = The number of turns of the coil.
âˆ†ÎŚ ∆đ?‘Ą
(2)