Magnetic effect of a current — Describe

Describe an experiment to identify the magnetic field pattern, including its direction, around a straight wire and a solenoid.

Pass a large current through a vertical wire (or a solenoid) placed through a horizontal card, then sprinkle iron filings on the card and tap it gently - the filings arrange themselves along the field lines, showing the pattern. Alternatively, place a small plotting compass at various points near the wire or solenoid and note the direction the needle points at each position to trace out the field lines and determine their direction.