®
ES-9080B
012-07227G
Basic Electrostatics System
9
Figure 7 shows the recommended method for using the proof plane to sample charge on a
conductive sphere.
Use the conductive knob on the end of the proof plane to sample the charge density inside a
hollow sphere (such as ES-9061 Conductive Shapes).
Faraday Ice Pail (ES-9042A)
The PASCO Faraday Ice Pail is shown in Figure 8.
Originally designed by Michael Faraday, it works on the
principle that any charge placed inside a conducting
surface will induce an equal charge on the outside of the
surface. It is an excellent product for sampling charges
and charge distributions. The PASCO version illustrated
above consists of two wire mesh cylinders, one inside the
other, mounted on a molded plastic bottom.
The outer cylinder is called the shield. It provides
complete visibility to the inside of the pail and, when
grounded, helps eliminate stray charges and AC fields.
The inner cylinder is the actual pail. The pail is mounted on insulated rods; the pail is 10 cm
in diameter and 15 cm high. When a charged object is placed inside the pail, but without
touching it, a charge of the same magnitude is induced on the outside of the pai (see Figure
6)l. An electrometer connected between the pail and the shield will detect a potential
difference. The greater the charge, the greater the potential difference. So even though the
electrometer will give readings of voltage, it is possible to use those values as relative charge
measurements.
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Figure 7: Proper use of a
proof plane to sample charge
Proof plane IS tangent to the
surface of the conductor.
Proof plane IS NOT tangent to
the surface of the conductor.
YES!
NO!
Figure 8: Faraday Ice Pail
Shield
Pail
insulators
