LEARNING GOAL: Electricity is based on electric charges. There are two kinds of charges: positive and negative . Positive and negative charges together cancel each other out. Opposite charges attract (pull together). (positive and negative attract.) Like charges repel (push apart). Positive and positive repel. Negative and negative repel.

How can you make electricity?
Cannot resolve external resource into attachment.
(from big box of art)
Put electric charge on balloons and see what they do.

### Engage

Electric charges are everywhere. They are very small - even smaller than atoms! - so you can't see them. There are two kinds of electric charge, called positive and negative .

Every object has a HUGE number of both kinds of charge. If the number of positive and negative charges is equal, they cancel each other out and the object is electrically neutral. But the object can have more positive than negative charges, or more negative than positive charges. Then it becomes either positively charged or negatively charged.

You can't create electric charges out of nothing. But when you rub a balloon on wool, positive charges collect on the balloon and negative charges collect on the wool. Then you can observe the force between them.

Draw a balloon and a wool sweater. Using the Stamp tool, put 10 signs and 10 signs on the balloon. Also put 10 signs and 10 signs on the wool sweater.

 DRAWING TOOL - with and stamps available. what size is best?
 help with using the stamp tool.

Is the balloon electrically charged, or is it electrically neutral?

• positively charged
• negatively charged
• neutral

Why do you think so?

Now drag some charges from the wool to the balloon. This is what happens when you rub them together.

Now is the balloon electrically charged, or is it electrically neutral?

• positively charged
• negatively charged
• neutral

Why do you think so?

### Materials

• Two balloons
• String
• Tape
• Wool sweater or shirt
• Construction paper, black and red
• Scissors

### Explore

Blow up two balloons, tie them shut, and tie on a piece of string about 50 cm long.

 Should they bother with this? Draw 15 plus signs on the red construction paper and cut them out. IMAGE Draw 15 minus signs on the black construction paper and cut them out. IMAGE Stick 5 plus signs and 5 minus signs on each balloon, near the opening. IMAGE Stick 5 plus signs and 5 minus signs on the wool sweater. IMAGE

Rub each balloon on the wool sweater. Rub all sides of the balloon, not just one side.
IMAGE

Hang each balloon near the sweater. What happens?

Hang the two balloons near to each other. What happens?

### Explain

When you rub a balloon on wool, some negative charges move from the wool to the balloon. Circle the right words to make these statements true.

The wool becomes (negatively / positively) charged.
One balloon becomes (negatively / positively) charged.
The other ballon becomes (negatively / positively) charged.

 Include?? or use drawing tool instead? To show this, move a paper minus sign from the wool to each balloon. Also move a paper plus sign from each balloon to the wool. Count the plus and minus signs on the balloons and the wool. Which has extra plus signs and which has extra minus signs? Which is positively charged and which is negatively charged? ANSWER BOX

Positive charges attract (pull toward) each other.
T F
Positive charges repel (push away from) each other.
T F
Positive charges attract negative charges.
T F
Positive charges repel negative charges.
T F

### Elaborate

Stick a piece of tape about 10 cm long to a table. Hold one end and quickly rip the tape from the table. This will move some extra charges to the tape – just like rubbing the wool and the balloon together.

IMAGE: DANGLING TAPE

Hold the tape near a balloon. What happens?

Hold the tape near the sweater. What happens?

Based on this observation, what is the charge on the tape?

• Positive
• Negative

Why do you think so?