Fieldlines

Place electric charges and see the field they make: lines that show which way a positive test charge is pushed, equipotentials that show where it takes no work to move, and the points where every push cancels. Drag a charge and the whole picture follows.

Click empty space to place a charge, drag a charge to move it, right-click or Shift-click it to remove it. With the picture focused: arrow keys move the selected charge (Shift for bigger steps), [ and ] shrink and grow it, F flips its sign, Delete removes it, . selects the next one, M switches point and line charges, G shows or hides the Gaussian surface, L turns launch mode on and off, O sends a test charge into orbit around the selected charge.

Point at the picture to read the potential and field there.

Scene

Charges

Gauss's law

Drag the square handle to move the surface and its rim to resize it. Solid rim: the field leaves; dashed rim: it enters.

Test charges
3

In launch mode, press on the picture and drag to set the launch velocity, then let go; a click without dragging releases the charge from rest. Test charges feel the field but do not change it.

Picture