Comprising of a circular ring made from non- magnetic silver aluminium  alloy wounded with  insulated copper wire. The ends of the wires are connected to the terminals which are fitted on the wooden base . A rectangular frame  made from  anodized  aluminium  bars  is  supported on wooden base,  aluminium  square bars  are  graduated up to 50 cm on both sides. A platform is provided which can moves on the rectangular frame along the axis of the coil. Permanent magnet compass box  has a hollow circular cavity at bottom to fit on this platform. Used To study the variation of magnetic field along the axis of a circular coil carrying current by plotting a graph.