Why is S=2*pi*r*l in the equation for induced voltage of a DC motor?

[kidsasd987]

TL;DR

V=P*Z*Phi*N/60a

Induced voltage of DC motor isV=Blv where B= phi/S
where S=2*pi*r*l and magnetic flux is phi=B*2*pi*r*l as shown in the picture.
that leads to the equation V=PZ*phi*N/60amy question is, why do we set S=2*pi*r*l
Shouldn't magnetic flux 0 because the magnetic flux of a closed surface is 0 according to Maxwell's equation.

Could someone please tell me why S=2*pi*r*l

 

[Baluncore]

Shouldn't magnetic flux 0 because the magnetic flux of a closed surface is 0 according to Maxwell's equation.

That is zero for the closed surface of a 3D volume. It is not true for the area of a rotating coil.

The induced voltage is the rate of change of flux through the coil.

2⋅π⋅n / 60 ; converts n RPM to angular velocity in radians per second.

You need to define your variables; S, r, l, P, Z, n, a;

 

[Babadag]

See:

https://circuitglobe.com/emf-equati...he emf of rotation,and represented as Er = Eb.

 

[kidsasd987]

The induced voltage is the rate of change of flux through the coil.

2⋅π⋅n / 60 ; converts n RPM to angular velocity in radians per second.

Thanks, I figured it out.