Electrostatics: The study of static electric charges. (Give your experience
eg. Combing hair, static cling, sweater over head; then define.)
CHARGING
FRICTION
CONTACT
INDUCTION
Charge: The net -ve of +ve charge that builds up on an object.
Charging: The process of building a net quantity of –ve or +ve charges on
an object.
Charging by Friction: Transferring electric charges from one
substance to another by rubbing. Depending on the materials being used the charges
will be different. Eg., acetate when rubbed with silk is positively charged. Ebonite
when rubbed with silk is negatively charged. The relative charge is determined by the
Electrostatic Series
Charging by Contact: Transferring charges from one substance to
another by touching. Same charge is received by the material being charged.
Charging by Induction: Transferring charges from one substance
to another without contact. Opposite charge is received by the material being
charged.
Reading Assignment: SNC1D1: pp. 460 -501; SNC1P1: pp.
252-273 in your Textbook.
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The Electrostatic Series – used to predict a charge
This can be used to predict what charged will be gained by two objects when they are rubbed
together.
weak hold on
electrons
strong hold on
electrons
acetate
glass
wool
fur or hair
silk
aluminum
cotton
paraffin wax
ebonite
plastic
rubber
gold
When two objects are rubbed together:
+
•
the one closer to the top of the
series will lose electrons and
become positive
•
the one closer to the bottom will
gain the electrons and become
negative
-
Example:
When clothes are put together in the dryer without fabric softener, they will rub against each other
and gain static electricity.
Suppose cotton socks are dried with a wool sweater.
The wool is closer to the top of the electrostatic series, so it has a weak hold on its electrons and
will lose them, gaining a positive charge.
The cotton is closer to the bottom of the list, so it has a strong hold on electrons, attracting those
from the wool. The socks will gain electrons and become negatively charged.
The positive wool sweater and the negative cotton socks have opposite charges and so they are
attracted to each other.
http://www.school- for-champions.com/science/static_materials.htm
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Mini-quiz to check your understanding
1. What happens to a material that collects electrons on its surface?
(a) It has a negative charge
(b) It has a positive charge
(c) It shoots off sparks
2. Rubbing which materials together would produce the most static electricity?
(a) Glass and rubber
(b) Cotton and ebonite
(c) Silk and aluminum
3. If you combed your hair with a plastic comb, which would give up its electrons?
(a) Your hair
(b) The comb
(c) Your skin, if it was dry
If you got all three correct, you are on your way to becoming a champion in science. If you had
problems, you had better look over the material again.
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Charging by Contact
On the following diagrams
1) Draw in the location of the negative charges
2) Show the direction of the movement of the negative charges
3) Shade in the position of the moveable leaf
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Charging by Induction
On the following diagrams
1) Draw in the location of the negative charges
2) Show the direction of the movement of the negative charges
3) Shade in the position of the moveable leaf
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Charging a Pith Ball
On the following diagrams;
i) Show how the negative and positive charges are arranged and
ii) Explain why the pith ball is first attracted then repelled from the rod
Discussion
1)
The neutral pith ball has equal number of (+) and (-) charges
2)
The negative (-) charges on the pith ball are repelled away form the rod. The positive (+)
charges on the pith ball are closer to the negative (-) charges on the rod than the pith balls
positive (+) charges. The pith balls positive charges are therefore attracted more strongly
than the pith balls negative (-) charges are repelled. Hence there is an overall attractio n
3)
When rod makes contact, surface negative (-) charges are able to move onto the pith ball,
giving it an overall negative charge.
4)
The pith ball is then repelled away from the rod.
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Static Electricity Lab
Time: 30 minutes
Purpose: You can produce static electricity from many common household materials. In this
activity, you can try some combinations of materials to find put which ones produce a static charge.
Problem: Which combination of materials results in the strongest electrical charge?
Materials: Styrofoam packing chips,
Group A
Group B
Plastic rulers
Paper towel
Soda Straws
Fur
Glass rods
Cotton
Ebonite rods
Plastic bag
Acetate strips
Sandwich wrap
Vinyl strips
Wool
Procedure:
1. Make the following table in your notebook.
2.
3. Choose an object in group A and rub it with a material from group B.
4. Bring the rubbed end close to a small pile of styrofoam packing chips and record the data in
the table.
5. Remove the styrofoam packing chips from the rod and hold them in your hand to remove
any charge from them.
6. Repeat steps 2-6 for different combinations.
7. When all the combinations of these materials have been tested, indicate in the table whether
the charge was strong, fair, poor, not present.
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Object A
Material B
# of chips picked up
Strength of charge
Questions:
1. Of all the combinations you tried, which pair of materials seemed to produce the most static
electricity when they were rubbed together? How did you decide this?
2. With which materials were you able to produce a static charge?
3. Why is it necessary to hold the styrofoam packing chips in your hand between each test?
4. If you have experienced any sma ll shocks at home or at school, describe the situation in
which they occurred. What pair of materials do you think might be responsible for
producing the static electricity?
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Radioactivity
Grounding
DISCHARGING
Shining
light
Discharge at
a point
DISCHARGING: if a charged object has its charge reduced, we say it is discharged
or neutralized. When a charged object is discharged by connecting to the ground, we
say that the object is grounded.
INSULATORS: These are substances in which elections do not move freely from
atom to atom. Some good insulators are rubber and plastic.
CONDUCTORS: these are substances which allowed electrons to move freely from
one atom to another. Some good conductors are copper and aluminum.
LIGHTNING RODS: These are placed on the tops of buildings to provide a lowresistance path to ground that can be used to conduct the enormous electrical
currents when lightning strikes occur.
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