To plot the magnetic field lines around a straight conductor carrying current: Pass straight conductor through a cardboard or glass-plate. And pass current.
From A to B direction in the upward direction. Sprinkle iron filings on glass plate. Tap the glass plate, the iron filing will arrange themselves in circles around the conductor along the magnetic lines of force. The magnetic fields are circular in nature. The direction of magnetic field can be detected with the help of magnetic compass and direction is found anti clock wise.
