Why Didn't the Disk Rotate in Maxwell's Magnetic Field Experiment?

[simplicity12]

Homework Statement

James Clerk Maxwell used an equipment to confirm the nature of the magnetic field around a long, straight conductor. he found that no matter how large the current through the wire, the disk did not rotate at all.

a. explain how this device can be used to determine the nature of the magnetic field around a conductor with a steady current.

Homework Equations

none

The Attempt at a Solution

By using the right hand rule.. the magnetic field is going to be horizontal and going in a counterclockwise direction... so why wouldn't the disk spin?

 

[Mindscrape]

So, you are supposed to talk about Maxwell's version of Ampere's law? Sorry, I don't really understand the problem. I think your picture is showing a current going through a wire, and a magnetic disk on the outside. You are supposed to talk about what happens outside the wire?