ELECTROSTATICS
at
CVCA
Created for CVCA Physics
By
Dick Heckathorn
25 February 2K + 5
1
Table of Contents
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Investigating Charge
Building an Electroscope
Electrostatic Series
Inv. Separating Charges on Two Spheres
Charging by Conduction
Charging by Induction
Ripping of Charges
Burning off Charges
Concept Dev 32.2
Demo Metal Rod Coat Hanger
Inv Charges in Petri Dish
Van de Graaff Generator
VDG How Dangerous is it?
Energy Units
Bulb lit using various size batteries
VDG Demonstrations
Electrophorus (Neg)
Electrophorus (Pos)
Lyden Jar
Safe Place Outside
Peanuts in Foam, Metal Can
Lightning Rods
2
1. Investigating Charge
Need 2 4-inch (or so) pieces of
Scotch magic tape with tab
a.
b.
c.
d.
e.
place each on table. A B
pull both off table.
bring them near each other.
What do you observe?
What else do you observe?
3
2. Investigating Charge
a. Place tape C on the table.
Then place tape D on top of it
b. Pull both off table (together).
c. Bring them near each other.
d. What do you observe?
e. Compare C and D to A and B
4
3. Investigating Charge
a. Place pieces of paper on the
table.
b. Bring the charged pieces of
tape near the paper.
c. What is the charge of the
paper?
d. What is the charge of the
tape?
5
3a. And The Charge Is….
a. How can we find out what the
actual charge is on the pieces
of tape?
b. Need some additional
information
c. Where can we get it?
d. From the text.
6
4. Construction
a. Build an electroscope
using a foam cup, straw,
scotch tape
b. Place piece of charged tape
on it.
c. Learn how to use it.
Skip Electrostatic Series
7
5. Electrostatic Series
a. Investigate rubbing one with
the other and then determine
the charge on each.
clear rod
Teflon
silk
cling wrap
Rabbits fur
wool
glass
rubber balloon
white rod (PVC)
8
6. Electrostatic Series
Materials tend to
receive electrons
and become
NEGATIVELY
CHARGED
Materials tend too
Lose electrons
And become
POSITIVELY
CHARGED
Teflon
Vinyl (PVC)
Saran wrap
Polyester
hard rubber
rubber balloon
sealing wax
Lucite
wood
paper
silk
cat’s fur
wool
nylon
glass
rabbit’s fur
Teflon
Vinyl (PVC)
Cling wrap
rubber balloon
silk
wool
Clear rod
Rabbits fur
glass
9
8-1 Investigation
Rub
white
with wool
Place
tworod
spheres
so that
they are touching.
11
8-3 Investigation
Bring white charged rod near
one of spheres.
12
8-4 Investigation
Separate the two spheres.
13
8-5 Investigation
Remove white rod
14
8-6 Investigation
Bring
small
sphere
Touch
small
sphere
tonear
white
whiteitrod.
rod until
repels
15
8-7 Investigation
Remove white rod using care
not to touch sphere.
16
8-8 Investigation
Bring small
Whatsphere
happens?
near each
large sphere.
17
8-9 Investigation
Explanation
18
8-10 Investigation
What’s
happening?
Brought
white
charged strip
near one of spheres.
19
8-11 Investigation
Spheres
were
charged:
Spheres
white
rodwere
was separated.
removed.
20
9. Method of Charging
Conduction
(wool, white rod, sphere on string)
a. Rub white rod with wool
b. Touch sphere to white rod until
it repels.
c. Check charge using the
electroscope.
21
9. Charging by Contact
Touch
Remove
spherewhite
to white
rod rod.
Charge of sphere same as rod
22
9. Method of Charging
Induction
(wool, white rod, sphere on string)
a. Rub white rod with wool
b. With sphere near the white rod,
touch sphere with finger
making sure the sphere does
not touch the white rod.
c. Check charge using the
electroscope.
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9. Method of Charging
Remove
finger.
Positive
Electrons
Electrons
charges
move
escape
to
remain
opposite
from
near
sphere
side.
rod.
Touch
with
finger.
Remove
rod.
Bring
sphere
near
negative
strip.
Induction
Explanation
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9. Method of Charging
Ripping Off Charges
(scotch magnetic tape)
a. Place tape on chair seat.
b. Pull tape from the chair seat.
c. Check charge using the
electroscope.
d. Can you find a surface that will
give the ripped off tape a
positive charge?
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9. Method of Charging
Burning Charges
(charged sphere on string, match)
a. Bring burning match near
charged sphere.
b. Check charge using the
electroscope.
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Concept Development 32.2
Homework
27
Demonstration
Metal Rod
and
plastic coat hanger
28
Demonstration
Wood Board
with
Teflon, Clear Rod and fur
29
Demonstration
Pop Cans
with
Teflon, Clear Rod and Fur
30
Demonstration
Pie pan, paper holes
with
Wool, fur or…
31
Investigation
Petri dish, paper holes
with
Wax paper, wool, cling wrap
and/or paper
32
Electrical Units
Electrical Charge  elementary charge
elem charge  charge on electron or proton
Electrical Charge  coulomb
1 coulomb  6.24 x 10 elem charges
18
1 elem charge  1.6 x 10
19
coulomb
33
Electrical Units
Electric Potential
Joule
energy
volt 

Coulomb ch arg e
34
Electrical Units
Current
Coulomb ch arg e
amp 

sec
time
36
Electrical Units
What is a volt times an amp?
volt  amp
Joule
volt 
coulomb
coulomb
amp 
sec
Joule coulomb Joule


 watt
coulomb
sec
sec
37
Electrical Units
What is an kilowatt-hour?
kilowatt  hour
1000 watt  hour
Joules
1000
 3600 sec
sec
6
3.6 x 10 Joules
38
Van de Graaff Generator
How is it constructed?
Go to
Classical Physics
D-44
39
Van de Graaff Generator
How dangerous is our
Van de Graff
generator?
40
Van de Graaff Generator
Spark jumps in dry air when

4 V
E  3x10
cm
Spark jumps _____ cm.
Electric Potential Difference is?
V = _____ volts
41
Van de Graaff Generator
Taken from our generator and data sheet.
How dangerous is a spark?
_______ volts x 10 micro-amps
= ____ watts
Spark lasts for 10 micro-sec
____ watts x 10 micro-sec
________ Joules
42
Van de Graaff Demo
Graphite Sphere
44
Van de Graaff Demo
Franklin Alert
45
Van de Graaff Demo
Fluorescent tube
47
Van de Graaff Demo
Charge a Person
48
Van de Graaff Demo
Christmas Tinsel
49
Van de Graaff Demo
Precipitator
50
Van de Graaff Demo
Aluminum Pie Pan
52
Kelvin Water Drop Generator
54
Electrophorus aluminum
plate,
scotch
tape,
Tape
cupfoam
to
aluminum
plate.
Remove
plate
from
foam.
Rub
with
wool.
Check
charge
on
foam.
Check
charge
on
plate
Touching
only
the
cup,
foam
cup,
piece
of to
foam,
wool
apparatus
oncheek.
foam.
byplace
touching
plate
No Charge on Plate
Setting Plate on Foam
55
Electrophorus Check
charge
on
Touch
bottom
aluminum
Remove
plateof
from
foam.
Place
apparatus
onfoam.
plate.
Remove
finger.
plate with finger.
How does this happen?
Touching Plate on Foam
56
Electrophorus Remove
plate
from
foam
‘-’
repelled
from
bottom
to
top
Foam
rubbed
with
wool
Finger
touches
plate
Place
plate
onleave
negative
foam
Charges
rearrange
Electrons
Wool
gives
‘-’
toplate
foam
Leaving
‘+’
behind
Finger
removed
from
plate
of plate
57
Student Investigation
Construct Lyden Jar
Materials:
35 mm film canister with lid
large paper clip
aluminum foil
water
60
Student Investigation
a. Charge electrophorus
b. While holding the film canister,
touch it to paper clip
c. Charge and touch to paper clip
8 to 10 more times
d. Then touch foil and paper clip
at the same time with finger
and thumb of one hand.
61
Demonstration
Dissectible Lyden Jar
62
Demonstration
Ice Pail
63
Discussion
Where is a safe place outside
when an electrical storm is
present?
Automobile?
Why?
64
Demonstration
Foam Can with plastic peanuts.
Metal can with plastic peanuts
Using V.d.G.
65
Discussion
How safe is an airplane?
66
Handout
Lighting Bolt Shatters Safety
Rule
67
Discussion
Why do some homes and barns
have lightning rods?
68
1. Demo: Use two aluminum
pans connected to van de
Graaff to demonstrate cloud
- set pointed object in bottom
of pan
69
Video
Lightning
70
Video
Static Electricity at Gas
Pump
71
That’s all folks!
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