Describe an experiment using a compass or iron filings to demonstrate the magnetic field produced by a current-carrying conductor.

Solution & explanation

Pass an insulated straight wire through card and connect a suitable low-voltage current source under supervision. Place compasses or sprinkle filings on the card. With current, compass needles trace circular directions and tapped filings form circles. Reverse current to reverse compass direction; increase current to increase deflection. Disconnect after observation to avoid unnecessary heating.