Погите "Ammeters and voltmeters" are made to operate on the same principle. 2. "Moving-iron instruments employ this effect". (General Question). 3. Moving iron instrument consists of "a coil, small piece of iron and a spindle" (what … of). 4. The repulsion type instrument has two pieces of iron. (…or…). 5. A pointer moves over a graduated scale. (Question-tag).