Insert a circular loop of copper wire through two holes drilled in a cardboard sheet. Connect the ends X and Y of loop with a battery, key, rheostat and ammeter as shown in adjoining figure. Sprinkle some iron filings on cardboard sheet. when a current is passed through the loop, the iron filings arrange themselves in a definite pattern, which gives the magnetic field pattern. The direction of field at the centre point can be obtained by placing a small compass needle there. The rule which helps to determine the direction of magnetic field is the ‘right hand thumb rule’. As per this rule let us consider our right hand with thumb stretched perpendicular to wrapped fingers. If now wrapped fingers give the direction of current flow in the loop then thumb will point in the direction of magnetic field. A galvanometer, an electric motor, an electric bell, an electric fan etc., are common devices that use current carrying conductors and magnetic fields.