Rubbing Cloth Woolen

Comprising two metal discs, with variable separation, supported on insulating pillars & provided with insulating handles on the ends of the adjustment slide rods, 4 mm sockets too are drilled onto the ends of the rods.
A rectangular glass plate is supplied which mounts in clips between the two discs & may be easily replaced by a plate of some other material to show the effect of different dielectrics. The whole is mounted on a polished wooden base.