Basic Electrostatics System
012–07227A
10
convenient to keep yourself grounded, by
continuously resting one hand on the upper
edge of the shield, or by direct contact with
the earth-ground connector.
NOTE: Make sure the electrom-
eter is connected to an earth-
ground, or the pail will not be
properly grounded.
Procedure 1A: Charging by Induction vs. Charging by Contact
1. Connect the electrometer to the Faraday Ice Pail as shown in Figure 1.1. Make
sure to ground the electrometer and the ice pail. The electrometer should read
zero when grounded, indicating there is no charge in the ice pail. Press the zero
button to completely remove all charge from the electrometer and the ice pail.
2. Always start with the voltage range in the higher setting (100 V) and adjust
down if needed. Analog meters are typically most accurate in the range of 1/3 to
2/3 of full scale.
3. The charge producers will be used as charged objects. Here is a general
procedure to follow when charging the producers:
• Always remove any stray charge on the necks and handles of the charge
producers by touching the necks and handles to the grounded shield. You
must also be grounded while doing this. It also helps if you breathe on the
neck of the charge producer, so that the moisture in your breath removes any
residual charge on the neck.
• Rub the white and blue surfaces together to separate charges.
• Keep in your hand only the producer you are going to use. Put the other
charge producer away, far from contact with any of the ice pail surfaces.
• Before inserting the charged disk in the ice pail, make sure you’re touching the
grounded shield.
4. Carefully insert the charged object into the ice pail, all the way to the lower half
of the pail, but without letting it touch the pail. Note the electrometer reading.
5. Remove the object and again note the electrometer reading. If the handle never
touched the pail, the reading must be zero.
Question to think about: Why was there a potential difference between the pail
and the shield only while the charged object was inside?
Figure 1.2 Grounding the Ice Pail.
lift from pail, then
from shield
touch both at
the same time