Primary and Secondary Coil is mainly used for teachers to demonstrate electromagnetic induction and verify Lenz’s law in middle school physics.  
Coil Experiment with Transformer Principles and Induction! The outer coil is 4-1/2" tall and 2-3/4" in diameter. The inner coil is 3-3/4" tall and 1-1/4" in diameter. The removable steel core with handle is 1/2" in diameter and 5-1/2" tall. All coils are wrapped with 20-gauge magnet wire with insulated binding posts as connectors. (5-1/2" x 3" x 2-1/2"; .75lb).

Physics School Lab Equipment Suppliers in India 

Ltekonline are the manufacturers of Primary and Secondary Coil Electromagnetic Lab used to demonstrate engineering principles in Engineering Colleges, Engineering Schools and Physics Lab Experiments for Engineering Teaching Lab in Universities