Flux density produced by a long coil (solenoid) Current flowing through a conductor produces a magnetic field. If the conductor is a long straight wire, then the field is distributed over a large region of space. If the wire is used to make a coil, the magnetic field is concentrated into a smaller space and is therefore stronger © D Hoult 2008
The flux density, Bc at the centre of a long coil, having N turns and of length L depends on
The flux density, Bc at the centre of a long coil, having N turns and of length L depends on the current flowing through the solenoid, I
The flux density, Bc at the centre of a long coil, having N turns and of length L depends on the current flowing through the solenoid, I the number of turns per unit length
The flux density, Bc at the centre of a long coil, having N turns and of length L depends on the current flowing through the solenoid, I the number of turns per unit length the permeability of the medium inside the solenoid
Experiments show that the flux density, Bc on the axis, at the centre of a solenoid is directly proportional to I directly proportional to N/L
I N Bc a L
I N Bc a L The constant of proportionality is µ (the permeability of the medium), therefore we have
I N Bc a L The constant of proportionality is µ (the permeability of the medium), therefore we have µ I N Bc = L
The flux density on the axis at the end of the solenoid is equal to
The flux density on the axis at the end of the solenoid is equal to Bc / 2
The flux density on the axis at the end of the solenoid is equal to Bc / 2
The flux density on the axis at the end of the solenoid is equal to Bc / 2