SACE Stage 2 Physics — Topic 2: Electromagnetism

Magnetic Field Lines

Compare the field around a permanent bar magnet (a magnetic dipole) with the field produced by a current-carrying solenoid. Toggle the interior lines to see how the field forms closed loops in both cases.

Controls

Display

Pole strength m

Magnet length

Polarity

Interior field

Current I

Number of turns N

Solenoid length

Current direction

Interior field

Bar magnet model Two opposite magnetic poles at the ends. Outside, the field runs N → S. Inside the magnet, the field runs S → N to close each loop.

Solenoid model A stack of current loops. Inside, the contributions add to give a near-uniform field along the axis; outside, the field looks just like a bar magnet's.