SOLUTION

The force acting on the moving iron piece in a Moving Iron (MI) instrument is independent of the direction of the current.

• MI instruments work because the iron is magnetized by the current flowing through a coil.
• The force on the iron is proportional to the square of the current.
• Squaring a number always results in a positive value, regardless of whether the original number was positive or negative. Therefore, the direction of the current doesn’t matter; the force will always be in the same direction.
• The force does depend on the magnitude of the current, the number of turns in the coil (which affects the magnetic field strength), and the shape of the iron piece (which influences how it interacts with the magnetic field).