---------> It is expected that students will explain the production, transfer, and interaction of static electrical charges in various materials.
Students who have fully met the prescribed learning outcome are able to:
Explain, with illustrations, how static charges are separated because of transfer between various materials
Describe types of static electrical charge (positive, negative) and no charge (neutral) with reference to atomic theory
Describe how the electric force between two objects depends on types of charge, size of charge, and the distance between the two objects.
photo: keyseeker@morguefile
RESOURCE
Static Electricity
A high school physics tutorial including four lessons: basic terminology and concepts, methods of charging, electric force and electric fields.
Antique technology for measuring static electricity
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PLANNING FOR ASSESSMENT /ASSESSMENT STRATEGIES
Demonstrate static electricity to students using a Vander Graff generator or Wimshurst machine, showing the charge is stationary until given a path to ground. Rub a vinyl strip with fur or wool and show how it affects an electroscope. Using several rubbing materials (paper, polyester, hair, silk, cotton, plastic,
etc.), have students working in groups rub strips of vinyl, plastic, wood, various metals, glass, plastics, carbon, and glass to see if the materials become charged.
RESOURCE:
How the Vander Graff generator works (short video) (diagrams)
Have students in each group record observations
of what happens when the Vander Graff
generator or the Whimhurst machine is used.
They should observe the response of the
electroscope and draw conclusions about whether
or not a charge is developed. Have students
define static charge.
• Ask students to complete a chart listing all the
materials used and whether or not each object
becomes charged. Students should determine
what types of objects do or do not get charged.
Notes and reports will be collected and evaluated.
Is their work complete, accurate, and well
organized?
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Review with students the atomic structure of
the atom, illustrating how atoms become
charged (i.e., by losing or gaining electrons).
Using positive and negative signs,
demonstrate how to sketch objects to show
whether they are positively charged,
negatively charged, or have no net charge
(neutral).
Ask students to draw in their journals atomic
models that show the nucleus with protons and
neutrons and electrons surrounding it.
• Have students draw atoms and ions for the first
20 elements in the periodic table. Look for
evidence that they can state the atomic number
and charge of each element.
• Ask students to write in their journals the answer
to the following question: What happens when an
atom gains or loses electrons? Answers should be
accompanied by diagrams that show positive,
negative, or neutral objects.
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Demonstrate the following for students: using
masking tape, hang two vinyl strips over a
ring stand and charge them by rubbing them
with wool. Ask students: Do they attract or
repel? Repeat, rubbing acetate with silk on a
second ring stand. Ask students to observe
what happens when the acetate strip is
brought close to the vinyl strip. Do they
attract or repel?
• Have students charge a balloon by rubbing it
against hair, then bringing it close to the
blackboard or glass.
• Conduct a demonstration with a Wimshurst
machine by turning it slowly then faster.
Have students observe in which case the
sparks jump a greater distance and suggest an
explanation.
• Have students use a piece of wool to rub a
vinyl strip, first gently, then more vigorously.
Each time, they should bring the strips to a set
distance from the ball of an electroscope. Ask
students the following:
- In which case do the leaves of the
electroscope move further apart?
- Where is the greater amount of work
done and which strip has the greater
charge?
Working in groups, have students record in their
journals observations from the experiments.
When assessing student journals look for
inclusion of the following:
- information on which objects attract or repel
- information about the effect of the size of
charge and how distance affects the force of
attraction or repulsion
- a record of situations when the force greater
or lesser
• Have students draw conclusions about attraction
and repulsion. Assess the extent to which they
recognize how the electric force between two
objects depends on types of charge, size of charge,
and the distance between the two objects.
