electrodynamometer

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An instrument that measures electric current by indicating the level of magnetic attraction or repulsion between a fixed and a movable coil, one of which carries the current to be measured.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An instrument, having a fixed and a moveable coil, that measures the power flowing in an electric circuit; a type of wattmeter.