Reference: EM29
Category: Electromagnetism
Purpose: Shows the effect of a dielectric on capacitance.
Description: Two parallel brass plates are mounted on a rail. (This is the same as for EM28) Connect one of the plates to the leaves and the other to the case of an electroscope. Charge one of the plates by stroking it with a Perspex or Teflon rod. (To control the divergence of the leaves if it excessive, hold a lighted match near the plates for a second or two.) There is a thick square-section glass slab on a Perspex base, held at the correct height. This needs to fit snugly between the two plates, so it is important to measure the correct distance before beginning. When this dielectric slab is introduced, the leaves fall because the potential difference is reduced and the capacitance is increased.
