Magnetic Field in Aluminum

Drop a magnet down a long small diameter aluminum tube, then drop a rock outside at the same time and see which one hits the floor first. This will show you magnets can affect aluminum. I don't know what type of meter you are referring to though...

i'm referring to the meter that the local power company uses to determind my power usage

http://en.wikipedia.org/wiki/Electricity_meter

In short, it's down to eddy currents.

See the description of an electromechanical meter in Wikipedia. Follow the link to eddy currents for more information.

JohnDG is correct. It happens due to the eddy current produced within the aluminum disc by the magnetic flux of the voltage coil and current coil of the energy meter. Not only the energy meter, all induction disc meters and relays operate on same principle. In some cases, instead of separate voltage and current coils, single voltage coil or current coil is used with splitting the flux.

- MS

You're not trying to slow it down, are you?

Study measurement instruments, i think you mean energy meter.It works under the principle of magnetic flux displacement.

Energy-meters are electronic in present days.

Why aluminium disc is used?. What will happen if iron ,copper or steel disc is used?.