Lesson 3

This lesson requires one balloon, a paperclip, two plastic straws and a clear plastic lid (PE).
Not provided are scissors, thread, paper, aluminum foil (lightweight), paper towel, wool sock.
This lesson explores electrostatic induction,
the pushing around of charged particles without making direct contact.

1 What did you do last time? 2 protons negative electrons positive friction neutral PRINT the word next
to the image on the next slide.
Charge - L3 fri pos ele neu neg pro
4 Notice the similarities! OPPOSITE POLES 
TWO electrical charges:

TWO magnetic poles:

Electrical charges and
magnetic poles
follow similar rules!
LIKE CHARGES REPEL! The rules for REPULSION are similar, too.
6 Charges and Poles
You CANNOT separate
a magnetic north pole
from a magnetic south pole.
You CAN separate
electrical charges.
You just did it with friction.
Each broken piece
always has two poles.
7 There is another way
to chase charges around . . .
FRICTION! Last time you transferred electrons
from your hair to a balloon
using simple . . .
8 To Explore INDUCTION one balloon scissors scrap of paper piece of
aluminum foil
you will need:
9 1 2 3 Cut the foil and paper
into tiny odd shaped chips.
Blow up
and tie
the balloon.
Or use paper circles from
a hole punch.
10 4 5 Charge the
balloon by
rubbing it
on your hair.
What happens?

Why are the pieces of foil
and paper attracted to the balloon?
Put the charged
over the paper
or foil chips.
11 REMEMBER When you rub the balloon
on your hair, negative electrical charges (electrons) from your hair are transferred to the balloon.
would the foil and paper
which are electrically NEUTRAL
be attracted to the balloon?
So CLEARLY you charged the balloon
13 And those small scraps JUMP
toward the surface of the balloon!
Even though these scraps are neutral,
electrons in the foil and the paper
are PUSHED AWAY from the surface
nearest to the negatively charged balloon.

So the surface of each small scrap
that is nearest to the balloon
becomes POSITIVELY charged.
14 Charging by Induction This is different than charging by friction.
Neither the foil nor the scraps of paper were rubbed.

Watch the electrons
in the small circles
of foil as the charged
PVC rods approach.
Does the charged rod
ever touch the foil
Do the electrons move back
when the charged rod is moved away
YES! The induced SEPARATION of charge is temporary. It lasts only
while the charged object is nearby.
NO! The charged rod
does not make
direct contact.
15 There is an attraction
between the balloon and the bits of paper and foil
even when the balloon is some distance away.

Like the force of gravity,
electrostatic forces can act between objects
even when the objects are not in direct contact.
16 1. Does the charged
object (body) make contact

2. Are electrons transferred

3. What happens to the charges
on the conductor when the
charged object is removed

4. Is the separation of charges
in the conductor only temporary

5. How does changing the charge on the
charged rod affect the electrons in the conductor
Charging with Induction: A Simulation Move the charged rod toward the conductor.
Use this simulation to answer the questions.
NO! The charged object does not make contact.
Notice the small gap.
NO! No electrons are transferred. The electrons return to neutral positions when the charged object is removed. Yes! It goes away as soon as
the charged rod is removed.
Induction creates a temporary but OPPOSITE redistribution or polarization of charge in the neutral object without contact. (You can change the charge on the rod here.)
17 Use INDUCTION to make pieces of foil or paper
dance like fleas in a circus.
FLEA CIRCUS! Find these items. small pieces of paper
or lightweight foil
of paper
facial tissue
(free of lotion),
paper towel or wool cloth
clear plastic lid
from the kit
18 Put the sheet of paper
on a desk or table.
Put the paper and foil chips
on the sheet of paper.
Cover the chips
with the clear plastic lid.
1 2 3
19 Try rubbing with a wool sock.
Does it work as well?
Vigorously rub
the plastic lid
with the facial tissue.
Keep rubbing and
watch how the chips of foil and paper jump up and fall down.
You made a F L E A ! CIRCUS 4 5 6
20 How does
the “flea” circus work
Unlike CHARGES attract! Click for answer. You charged the lid using friction.
The negatively charged lid in turn, INDUCED a charge
in the bits of paper or foil.
The electrons moved AWAY from the lid.
The protons on the chips facing the lid
were then pulled toward the lid itself BECAUSE . . .
21 Charging with Induction FIRST click on Electra below. AFTER she finishes,
click on the red button.
You can hit pause at any time or replay to start over. 1. Zero. 2. Friction. 3. No.
4. No. It was temporary.
5. Unlike charges attract.
22 Charge - Review! 23 How many types of
charges are there
Do like charges
attract each other
With induction, are electrons transferred With induction,
does the charged object have to touch the neutral object
1 2 3 4 5 Is an induced
charge only
NO! The charged object does not make contact. TWO: negative and positive NO! They repel. YES! It is only
NO! No electrons
are transferred.