Finding the Length of a Conducting Armature in a Magnetic Field

[Titan]

I have a problem, to do with conductor in a magnetic field. The question says to find the length of the conducting armature with the magnetic flux.

I was planning on using the formula F= BIL. I have alright calculated the flux density and got the current, however the force is not given so I can't transpose the formula.

is there another method I can could uses?

 

[genneth]

Could you reproduce the question in its entirety? I'm not sure what the question you're trying to solve actually is.

 

[Titan]

Could you reproduce the question in its entirety? I'm not sure what the question you're trying to solve actually is.

the question is

DC motor requires to produce a maximum output torque of 7.5 x 10-3 Nm. The design must incorporate an armature (rotor) situated in a uniform magnetic field supplied by a solenoid. Solenoid produces a total magnetic flux of 3 x 10-5Wb acting perpendicularly across a rectangular field 30mm by 20mm. The gap between the two poles can be set between 25mm and 35mm without losing any total flux. The current flow in the armature coil can be between 0.6A and 1.2A.

Design an armature that will produce the required torque given the specification stated. I must present a solution and sketch of the design that clearly shows:

A) Length of the conducting armature within the magnetic flux
B) Number of turns of the wire on the armature
C) Diameter of the armatures
D) Gap between the poles
E) All calculations that support the final design solution