Working Principle of Attraction Type Moving Iron Instruments

Working Principle of Attraction Type Moving Iron Instruments Points : Working Principle of Attraction Type Moving Iron Instruments The attraction type instrument works on the principle of attraction. If a small piece of soft iron is pivoted or mounted near a coil and current is passed through the coil, the iron piece or vane is attracted and tends to be pulled in to the stronger magnetic field inside the coil. The soft iron is attracted for either direction of current in the coil, so the principle may be used as the basis of an a.c. instrument. The force is dependent upon the current (actually upon i²), hence the addition of a control spring, pointer and scale make possible a measuring device.