Electromagnetism/Permeability Question

[blarginsnarf]

Homework Statement

An electromagnet is able to exert a force of 1.5x10^2 N when lifting an object. The electromagnet has 1000 turns, a current of 1.5A, and a material in the core with a relative magnetic permeability of 2.0 x 10^3. What force will the electromagnet exert if the following changes are made, each considered separately?

a) The current is increase to 6.0 A.

b) The number of turns in the coil is increased to 1400 without increasing the length of the coil

c) All of the above changes are considered simultaneously.

Homework Equations

My textbook shows absolutely NO equations relating to permeability. Thus, I literally have no idea what to do :S

 

[Simon Bridge]

Doesn't ask you about permiability.
You just need to know about proportionality.

a) the current is 4x
b) you have 1.4 (that's almost the square-root of two) times the turns per unit length.

You have equations that relate how #turns and current to an electromagnet.
What's the problem?