Drag the potential difference slider to change the potential difference, and thus the current (it can be negative as well as positive).
Toggle the 'Show magnetic field lines' button to show/hide the field lines; the number and density of field lines increases as the current increases.
Toggle the 'Show field direction' button to add an arrow to the field lines to show their direction.
Toggle the 'Current type' button to switch between D.C. (default) and A.C., this can be used to illustrate how A.C. leads to continually changing magnetic fields. The frequency of the A.C. can be adjusted with the 'A.C. frequency' slider.
Click the 'Add compass' button to add a compass to the field lines, which can be dragged around to different positions; you can add up to 12. Click the 'Remove compass' button to remove the compasses.
Mode specific instructions:
Switch modes between 'Straight wire' and 'Solenoid' by clicking at the top of the settings panel.
In 'Straight wire' mode:
Toggle on the 'Moveable magnetic fields' option to see the field lines for one specific electron moving as the electron moves, to make the point that moving charges create magnetic fields.
Toggle on the 'Number of moving fields' option to 'All' to see the field for every electron (Note: this can cause slow-down).
In 'Solenoid' mode:
Drag the 'Number of coils' slider to change the number of coils and see the effect on the field strength.
Notes:
• The purple circles represent electrons moving in the wires.
• This is an illustration rather than a simulation; the field lines adjust to illustrate key principles rather than accurately modelling the underlying physics.