Describe an activity with a neat diagram to demonstrate the presence of magnetic field around a current-carrying straight conductor.

Describe an activity with a neat diagram to demonstrate the presence o

1.	Describe an activity with a neat diagram to demonstrate the presence of magnetic field around a current-carrying straight conductor.
Answer» Solution :Take a long straight thick copper wire and insert it through the centre of a plane cardboard. Cardboard is fixed so that it is perfectly horizontal and the thick wire is in VERTICAL DIRECTION. Prepare an electric circuit consisting of a battery, a variable resistance, an ammeter and a plug key. Connect the copper wire in the circuit between the points X and Y. Sprinkle some iron-filings uniformly on the cardboard. Put the plug in key K so that a current flows in the circuit. Gently tap the cardboard using a finger. We observe thatthe iron-filings ALIGN themselves forming a pattern of concentric circles around the copper wire. These concentric circles represent the magnetic field lines. Direction of field lines is DETERMINED by the use of a compass needle. If current is flowing vertically downward then the magnetic field lines are along CLOCKWISE direction. If current is flowing vertically upward then the field lines are along anticlockwise direction.