Lesson 2

This lesson requires 3 balloons, one paperclip and two plastic straws.
Thread, scissor and tissues or paper towels are not provided.

Students discover that objects with opposite charges attract,
while objects with like charges repel. Simulations and questions follow.

1 What did you do last time? 2 protons negative electrons positive charge neutral PRINT the word next
to the image on the next slide.
3
Charge - L2 cha pos ele neu neg pro
4 Blow up
and tie
the balloon.
1 Let’s explore CHARGE! one balloon scissors You will need: thread
5 2 Stand in front of a mirror
to watch as you rub
the balloon vigorously
on your hair.

Be sure your hair
is clean and dry.
THIS WORKS BEST
IN DRY AIR.

Slowly pull the balloon
away from your hair.
What do you notice?
6 ATTRACTION? On a dry day especially,
strands of hair should stick
to the balloon.
WHAT CAUSES THIS
7 As you rub the balloon against your hair,
electrons are transferred
from your hair to the balloon.

This is because the latex balloon
has a greater affinity for electrons
than your hair does.
CHARGE! What causes your hair
to stick to the balloon?
8 OPPOSITE CHARGES ATTRACT! Objects with
opposite charges
attract each other . . .
The balloon becomes
NEGATIVELY charged.
Your hair becomes
POSITIVELY charged.
9 REMEMBER: When you rub the balloon
on your hair, negative electrical charges (electrons) from your hair are transferred to the balloon.
10 What do you think will happen if you place
two NEGATIVELY charged balloons
next to each other?

Will they attract each other, too?
TEST IT!
11 NOTE: This works best
with smaller balloons.
(5 inch or 12 cm)
1 2 3 To test this,
blow up
and knot two
fresh balloons.
Make sure
that they are
fully expanded
with air.
Tie about 12 inches
(30 cm) of thread
to each balloon.
Rub both
balloons
vigorously
on your hair.
12 Like CHARGES REPEL! REPULSION! The electrostatic repulsion PUSHING the balloons apart has to overcome the force of gravity PULLING
downward. To confirm this, try the very same experiment with smaller, thinner, lighter balloons.
Is the REPULSION more pronounced now? WHY? It takes less force to push the lighter balloons apart.
Hold one of the balloons by its string and
slowly move it toward the other balloon.

What happens?

Does one balloon avoid the other?
13 What is happening
between the two balloons
Like CHARGES REPEL! Click for answer. As you rub each balloon against your hair, electrons
are transferred from your hair to the balloons.

Both balloons become NEGATIVELY charged.

Objects with the same charge repel each other.
14 Here is another experiment that shows that: thread scissors facial tissue
(free of lotion)
or paper towel
paper clip 2 plastic straws You will need: Like charges REPEL!
15 Insert one straw
through the
inner loop
of the paperclip.
Tie a piece
of thread to
the paperclip.
Dangle the
first straw
by the string.
WHY What happens as you
bring the charged straw
near one end of the
dangling straw?
Rub both
straws with
the tissue
or paper towel.
Like charges REPEL! Click
for
answer.
1 2 3 4
16 You now know there are
two types of charge: PLUS and MINUS.
AND you learned these RULES for charges:
nucleus
with protons
LIKE CHARGES REPEL! OPPOSITE CHARGES ATTRACT! electron electron electron
17 Positive charges
attract negative charges
and repel other
positive charges.
Negative charges
attract positive charges
and repel other
negative charges.
Describe how
negative charges
interact with
OTHER positive
and negative charges
Describe how
positive charges
interact with
OTHER positive
and negative charges
1 2 Click
for
answer.
Click
for
answer.
18 Charging with Friction 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. Postive
4. Unlike charges attract.
5. Like charges repel.
19 Charge! 20 How many types of
charges are there
Do like charges
attract each other
What about two unlike charges If an object has
a googol plus charges
and a googol minus charges,
WHAT is the total charge
1 2 3 4 5 What is the charge of an object that was neutral but has lost electrons through friction ZERO!
It is NEUTRAL.
TWO: negative and positive NO! They repel. They attract. It is positively charged.
21