3B Scientific Electroscope User Manual

3B SCIENTIFIC® PHYSICS

U17250 Electroscope

Instruction Sheet

6/03 ALF

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The device is used for an introduction into the funda­mentals of electrostatics and for displaying DC and AC
voltages as well as demonstrating the operating prin­ciples of high voltage meters according to Braun.

1 Sphere with 4-mm plug

2 Insulator

3 Shielding ring

4 Baseplate

5 Capacitor plate with 4-mm plug

6 Capacitor plate on insulating rod

7 4-mm socket

8 Support with pointer

2.1 Scope of supply

1 Electroscope
1 Sphere with 4-mm plug
1 Capacitor plate with 4-mm plug
1 Capacitor plate on insulating rod

1. Safety instructions

• Make sure that the insulator is always clean and
dry. If necessary use alcohol or spirits for cleaning.

• At high humidity and after transporting the unit
from a cool room into a warmer one, dry the elec­troscope in a stream of hot air (e.g. a hair dryer).

2. Description, technical data

The electroscope consists of a metal baseplate on which
the iron shielding ring for defined field distribution is
mounted. The iron ring is equipped with a 4-mm socket
for earthing purposes. The support for needle with
pivot bearing is attached electrically insulated to the
shielding ring. The pointer is suspended asymmetri­cally and so its weight delivers the restoring moment.
Inside the electrically conductive insulator at the up­per part of the device there is a 4-mm socket for mount­ing the sphere and capacitor plate.
For demonstration experiments the electroscope is suit­able for shadow projection using a point source light.
Diameter: 130 mm

3. Operation

The electroscope is charged using friction rods stati­cally charged by various friction-inducing materials
(e.g. U11053), or using a high-voltage power supply unit
(e.g. U21060).

3.1 Charging up the electroscope by touching it
with a statically charged body

• Attach the sphere or capacitor plate to the elec­troscope.

• Rub the friction rod with the suitable material (PVC
or acrylic rods e.g. with plastic foil).

• Touch the sphere or capacitor plate with the
charged rod. The pointer deflects.

• Remove the friction rod, the pointer remains de­flected.

• Touch the sphere with your hand. The pointer re­turns to normal.

• When a high-voltage power supply is used then
attach the capacitor plate to the positive pole of
the power supply unit. Connect the negative pole

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with the earth socket on the power supply and
with the earth socket on the electroscope.

• Use a charge spoon (e.g. U11051) to draw a charge
from the capacitor plate and transfer it to the elec­troscope.

3.2 Using electrostatic induction to charge up the
electroscope

• Approach but do not touch the sphere (or capaci­tor plate) with the statically charged friction rod.

The pointer deflects.

• Remove the friction rod. The pointer returns to
normal.

• Again approach the sphere with the statically
charged friction rod. Once again the pointer deflects.

• Briefly touch the sphere with your finger to dis­charge it. The pointer deflection disappears and
returns to normal.

• Now remove the friction rod. The pointer again
shows deflection.

Fig. 1: Charging the electroscope using the high-voltage

power supply U21060

Fig. 2: Charging the electroscope using a statically-charged

friction rod

3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany • www.3bscientific.com • Technical amendments are possible

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