Physical Science Lab Exercise
Static Electricity
Name_____________________________________________________________________________________
Lab Partner(s)______________________________________________________________________________
Date______________________________________________________________________________________
Lab Station Number_________________________________________________________________________
Materials List:
2 Ebonite rod(s), (large clear plastic rods also, Fur or wool cloth strips, small piece of a plastic drinking
straw covered with aluminum foil hanging from a sewing thread, long glass rods, silk strips of cloth,
ring stand to support an ebonite rod, electroscope, string, scissors, right angle clamp.
Objectives:
1) Define “static electricity”
2) Describe how to build up negative and positive static electrical charges (separately).
3) Describe how - & + charges interact.
4) Induce a static charge on an object
5) Describe how a neutral object behaves in the close proximity of a statically charged object.
Description of Concepts:
Everything contains electrical charges. Most of the time, there is an equal amount
of positive and negative charges on most objects and they are neutral. Certain
substances can obtain a static electrical charge with friction. This is static electricity.
During the wintertime especially in northern climates, the humidity is usually low and
static electrical discharges can be made by just shuffling your shoes on a carpeted
surface and then extending your finger to touch something (especially metal). The zap
of electricity is just the two differently charged objects becoming neutral. There is a
transferal of charges from one object to another.
If a body is negatively charged by friction it is because the body has an excess of
electrons; if a body is positively charged it has a deficiency of electrons. In the study of
static electricity a good general rule to remember is: Positive charges do not move
from one body to another body.
Neutrally charged objects have an equal amount of electrons and protons.
Electrons can move in a neutral object. When a neutral body is touched by a charged
object, the neutral body receives the same charge that the charged object possesses.
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Procedure:
Here is a list of things that need to be done to explore all the different possible reactions
between the negatively charged ebonite rod (or large clear plastic tube), the positively
charge glass rod, the neutral “pith ball”, and the neutral electroscope, For each one of
these mini-experiments, the student is expected to explain the specific reason for the
observed results in terms of the movement of the electrons. Clearly identify the charge
that the neutral object receives in every case.
1) Neutralize the pith ball by touching and holding it for a few seconds between your
fingers Charge up the ebonite rod (or long clear plastic tube) with fur or piece of wool
and bring it close to the pith ball. Observe and record the effects. Allow the pith ball to
come into contact with the charge ebonite rod. Observe and record the effects.
2) Neutralize the pitch ball as before. Charge up the long glass rod with the silk cloth.
Use caution! Do not drop the glass and be cautious while charging it up, don’t injure
your hand in the process. Bring the rod close to the pith ball, observe and record the
effects, then allow them to touch and observe and record the effects.
3) Suspend an ebonite rod with a string, if the lab instructor has not already done this
already. It should be balanced. Charge up the pointed end of the suspended rod, but
only that one half of the rod. Charge up the other ebonite rod that is not suspended..
Bring the two charged ends close, but not touching. Observe and record the effects.
Bring the charged end of the non-suspended rod close (but not touching) the neutral
end of the suspended rod. Observe and record the effects.
4) Repeat with a charged glass rod – observe and record the effects of bringing it close
to the charged end of the suspended ebonite rod and close to the neutral end. Do not let
them touch!
5) Neutralize the electroscope by putting a finger on the top of the scope and leaving it
there for a few seconds, then remove the finger. Charge up the ebonite rod (or large
clear plastic rod) and bring it close to the top of the ‘scope and observe and record the
effects. Allow the rod to touch the top of the scope. Don’t just tap the top, allow full
contact and more the rod until the leaves of the scope react.
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6) Neutralize the electroscope as before and repeat the entire step 5 with the glass rod.
Close, then touching. Observe and record the effects for both situations carefully.
7) Induction: When an object has been charge by induction, the object receives the
opposite charge of the charging body. To induce a charge on the electroscope, start
first by neutralizing the electroscope. Charge up the ebonite rod (or large clear plastic
tube). Bring it close (without touching the rod to the scope) to the top of the
electroscope. Observe and record the effects. While the rod is close, bring a finger from
the other hand and touch the top of the scope and leave it there for a few seconds.
Observe and record the results. Then, first remove the finger, then remove the charging
rod. Observe and record the effects.
8) Explain how you would induce a negative charge to an electroscope. (Don’t actually
do this, it is a through experiment)
Special Note: After each of these experiments, the student is encouraged to use the
other charge rod or glass to confirm the charge on the object. For example, if the object
was charged by the ebonite, use the glass rod (charged) to see the effects by bringing it
close (not touching!) to the charged object. Recall that like charged objects replel and
opposite charges attract. This would be a verification of the charge on the object by a
separate observation.
Analysis and lab report notes:
As you can see, this is not the typical lab experiment. No excel sheet, no quantifiable
results. But, there are a LOT of observations and conclusions to be drawn. By just
doing this lab as it is written, and answering the questions, that should be plenty of
information that can be summarized and put into the procedure and conclusions.
So, write up the lab report with the Introduction, Purpose, Procedure (summarize, but
make it complete), No data, but lots of Results and Conclusions! One page, one side!!!
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