3B Scientific Piezoelectric Charge Source User Manual

3B SCIENTIFIC

Piezoelectric Charge Source U8490210

Instruction sheet

01/11 SP/ALF

®

PHYSICS

1 Button
2 Earthing lead
3 Charge-carrier
4 Protective cap

1. Description

The piezoelectric charge source enables safe volt­ages to be generated for electrostatic experiments.

The instrument is, in principle, a piezoelectric gas­lighter that is adapted for the special requirements
of electrostatic experiments. For that reason it is
fitted with a shortened earthing shell onto which a
lead is soldered.

The heart of the charge source is a piezoelectric
crystal of lead-zirconate-titanate (Pb(Zr,Ti)0
ing the button causes a separation of charges, Q, in
the crystal. In the absence of an external circuit,
the voltage thus produced is limited by the break­down voltage and the intrinsic capacitance C
the crystal. When an external capacitance C
present, the resulting voltage is: U = Q/(C

2. Technical data

Voltage: 4.5 kV max.
Cable connection: 4 mm plug
Dimensions: 240x30x40 mm³ approx.
Weight: 100 g approx.

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3. Operation

When the button is pressed, a positive charge is
produced at the tip, whereas if pressure is released
after the instrument has already been earthed, a
negative charge is obtained.

To positively charge a capacitor (e.g., a conducting
sphere), proceed as follows:

• While pressing the button, touch the capacitor

with the charge-carrier.

• Earth the charge source while it remains in

contact and release the button.

• If necessary, repeat the charging process until

the desired charging voltage is obtained.

Considered from a physical standpoint, the process
is as follows: When the capacitor is touched, the
positive charge produced by the piezoelectric crys­tal is shared between the crystal and the external
capacitor in proportion to their capacitances. Only
if the capacitor has a very large capacitance
(>>100 pF) will the charge be completely trans­ferred to the capacitor. When the pressure is re­leased, the negative charge generated is dissipated
through the earthing cable, and the crystal is then
uncharged.

Elwe Didactic GmbH ▪ Steinfelsstr. 5 ▪ 08248 Klingenthal ▪ Germany ▪ www.elwedidactic.com

3B Scientific GmbH ▪ Rudorffweg 8 ▪ 21031 Hamburg ▪ Germany ▪ www.3bscientific.com

Subject to technical amendments

© Copyright 2011 3B Scientific GmbH