The SEP charge indicator allows for easy rapid investigation of electrostatic effects.
When it is moved towards a charged object, one of the LEDs will light up – red indicates that the object is positively charged, and green indicates a negative charge. When a polythene rod is rubbed using a piece of cloth, for example, the green LED comes on when it is brought near the polythene, and red near the cloth.
This demonstrates how negative charge has been transferred from the cloth to the rod.
[Needs a PP3 9V battery, not included.]