Describe an activity to obtain magnetic …

Aim: To study the magnetic field due to a straight current-carrying conductor.
Apparatus Required: A thick conducting wire, battery, rheostat, magnetic needle, ammeter (0-5 A), key, a cardboard, a stand to hold the wire, iron filings and sprinkler of iron filings.
Procedure: Attach the thick wire through a hole at the middle of the cardboard and clamp it in a stand. Attach the ends of the wire through a key, variable resistor and an ammeter. on either side of a battery and hold it vertically and perpendicularly to the board. Spread the iron filings uniformly on the cardboard and place the magnetic needle on the board. Close the key and tap the cardboard slightly and observe the orientation of iron filings. Magnetic field around a straight conducting wired concentric circles indicate the field lines
Observation: Just on closing the key, the iron filings are aligned in the pattern of concentric circles around the wire. Conclusion: A current-carrying conductor is a source of magnetic field. The magnetic field is in the form of concentric circles whose centre lies on the wire.