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What do you already know about electricity?
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1. Here are two circuits, each with one battery and two light
bulbs. Answer the questions about these two circuits.
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B |
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Press the Right Arrow below to go to the next page.
Press the Right Arrow below to go to the next page.
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| Congratulations! You have completed this section. |
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1
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In this activity, you will place electric charges on balloons
and see what they do.
Then you will compare this to a model of charged balloons. |
I've played with balloons at parties. I've rubbed them on my hair and clothes.
As you experiment with the balloons, look for patterns.
Try to picture these charges in your mind as you work with balloons.
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Engage
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and negative.
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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.
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| But an object can have slightly more positive than negative charges. Then it becomes positively charged. |
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Or it can have slightly more negative than positive charges.
Then it becomes negatively charged.
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signs and 5
signs on the balloon. Also put 5
signs and 5
signs on the wool sweater.
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Explore
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Explain
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Good scientists make careful observations.
Some negative charges moved from the wool to the balloon. You need to know how charges react to one another.
Think about the experiment you did with the balloons. Your observations should help you answer these questions.
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This model was created using a modified PhET model.
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This model was created using a modified PhET model.
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This model was created using a modified
PhET
model.
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Now check Two Balloons and rub each one on the sweater. Then
hide the wool sweater by unchecking the Show sweater box.
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This model was created using a modified PhET model.
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Elaborate
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I've felt and seen the small spark!
During this activity, we've been thinking about positive and negative charges. I think the answer here has something to do with charges.
Sparks are caused by moving electrical charges.
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2. Here's a picture of your experiment with hair and a
balloon. Use the positive and negative stamps to show where
you think the charges are on the balloon and the hair.
Take a snapshot of your drawing. |
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Congratulations! You have completed this activity.
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How do electric charges behave?
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In this unit, you will explore how electricity is moved around and transformed into other forms of energy. |
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You have completed the Introduction. Click on the UDL HOME button below.
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What is electricity?
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1
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Read the story of "The Electrical Birthday Party" by using the forward and back arrows below. |
Can you predict what the story will be about?
Read the title and look at the picture for clues.
I predict the story will be about a birthday party and electrical
charges.
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Chapter 1
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2
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A funny thing happened when Chen rubbed the balloon on his sweater. The balloon stuck to the sweater! Some of the other children saw what Chen was doing and wanted to try it themselves. Soon everybody was trying to see how many balloons they could stick to their sweaters.
Happy birthday, Chen! Have you ever had balloons at a birthday party?
Make a drawing in your mind about what the children are doing with the balloons.
The story says the children are rubbing balloons on their sweaters.
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Chapter 2
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3
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Margaret was happy to be invited to Chen's birthday party, but now she was bored. There were no girls her age here. In fact, Chen hadn't invited any other girls to his party! At first, Margaret had wanted to come to see what he got, but now she was sitting all alone with nothing to do. No one was paying attention to her, and no one wanted to play with her. They just wanted to play with their stupid balloons!
Margaret had an idea. "If all these balloons stick to sweaters," she thought, "maybe I can get them to stick to each other! Then I could make a big bunch of balloons and float away!"
Margaret found a blue balloon taped to the wall. She pulled the tape off and held the string in her hand. Then she found a yellow balloon attached to the ceiling. She pulled that one loose and held its string in her other hand.
Margaret rubbed the blue balloon on her sweater. It stuck to her sweater. Then she rubbed the yellow balloon on her sweater. It stuck, too. Then Margaret pulled the balloons off her sweater and tried to get them to stick to each other.
Margaret was bored, so she did an experiment.
What do you notice about Margaret's experiment?
I notice that Margaret's first idea was not right. She thought that
because the balloons stuck to sweaters, they would stick to each
other.
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Chapter 3
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4
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Elvira was a friend of Chen's family. Margaret liked her a lot. She had flaming red hair and green eyes and she wore funny-looking clothes and talked in a loud voice. But she could answer any question and she sometimes showed Margaret and Chen some pretty amazing things. And best of all, she was right here in the house! She had come to Chen's birthday party and now she was talking to the grownups in the living room while Chen and his friends played with their balloons and never even noticed that they repelled.
Margaret ran to the living room with her balloons. Chen's mother and father were there with Elvira. "Look what I discovered!" she said. She pointed to the balloons. "They repel each other," she said, "but they're both attracted to my sweater."
"That's nice, dear," said Chen's mother.
"What were you expecting to happen?" asked Elvira.
"I thought when I rubbed them on my sweater the balloons would get all sticky," said Margaret. "But that didn't happen. They don't stick to each other. See, they push each other apart!"
"That's because they both have the same kind of charge," said
Elvira. "If you want, I'll show you." She stood up and looked at
Chen's parents. "Will you excuse me a moment?" she said. She picked
up a large cloth bag in one hand. Then she turned to Margaret and
waved her other hand in a grand gesture. "Take me to your balloons!"
she cried.
It must be fun to have a friend like Elvira, who can answer any question.
What does Elvira tell Margaret about the balloons?
Elvira tells Margaret that the balloons have the same kind of charge, and that she will show Margaret those charges.
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Chapter 4
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"Hush!" said Elvira. She said it rather quietly, but somehow everyone heard her. They all quieted down and looked at Elvira.
"Margaret has something to show you," said Elvira. "Show them, Margaret."
Margaret showed them how the balloons pushed each other apart. "They repel," she said, "but I don’t know why."
"I'm going to show you all why," said Elvira. "Watch!"
She reached into her cloth bag and took out a strange-looking object. It looked kind of like a magnifying glass, but it was much bigger than any magnifying glass Margaret had ever seen. The lens was square instead of round and it was almost as big as Margaret's head. The handle was long and thick and it had about a dozen buttons and switches on it.
"I've seen one of those before," said Chen. "We have them in school. It's called a magnifying glass."
"Ah, but this magnifying glass is different!" replied Elvira. "Wait till you see what it can do!"
Can you predict what Elvira's magnifying glass will do?
Look at the story for clues about what the magnifying glass might do.
Elvira had said she would show Margaret the charges on the balloons. I predict that's what the magnifying glass will do.
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Chapter 5
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"What are electric charges?” asked Chen.
"I know, I know!” said Tommy. Tommy was one of Chen's friends who had been invited to the party. He waved both hands in the air and jumped up and down, but Elvira ignored him.
"Electric charges come in two kinds," she said, "positive and negative. Everything in the world is made up of electric charges and there are usually just as many positive charges as negative charges."
Margaret asked, "Can we see them through your magnifying glass?"
"Not unless they are separated," said Elvira. "When the positive and negative charges are together, they cancel each other out. They become invisible. You can't see them, even with this special magnifying glass."
"So what good is that thing, anyway?" said Chen. "If it can't see charges, what is it good for?"
The story tells us about charges.
Imagine in your head what charges might look like if you could see them.
Elvira says there are positive and negative charges. I imagine plus and minus signs.
"It can see them," said Elvira. "Weren't you listening? We just have
to separate the negative charges from the positive charges, so they
won't cancel out."
"And how do we do that?" said Chen. "You've been doing it all afternoon," said Elvira. "Whenever you rub a balloon on your sweater, some of the charge separates. Here, I'll show you. Give me a balloon."
Elvira rubbed the balloon on Chen's sweater and then she put the magnifying glass up close to the balloon. Chen looked through the magnifying glass. "I see a bunch of little tiny minus signs on this side of the balloon!" he announced. He turned the balloon over. "But there are no minus signs on the other side."
"That's because you only rubbed one side of the balloon," said Elvira. "The charge only separates where you rub."
"Those minus signs represent negative charge," said Elvira. "When you rubbed the balloon, you separated the two kinds of charges. The negative charge moved to the balloon, leaving the positive charge behind on the sweater."
"And how do we do that?" said Chen. "You've been doing it all afternoon," said Elvira. "Whenever you rub a balloon on your sweater, some of the charge separates. Here, I'll show you. Give me a balloon."
Elvira rubbed the balloon on Chen's sweater and then she put the magnifying glass up close to the balloon. Chen looked through the magnifying glass. "I see a bunch of little tiny minus signs on this side of the balloon!" he announced. He turned the balloon over. "But there are no minus signs on the other side."
"That's because you only rubbed one side of the balloon," said Elvira. "The charge only separates where you rub."
"Those minus signs represent negative charge," said Elvira. "When you rubbed the balloon, you separated the two kinds of charges. The negative charge moved to the balloon, leaving the positive charge behind on the sweater."
"So the sweater should have a bunch of plus signs on it?" asked Chen.
"Let's find out!" said Elvira. She held the magnifying glass close to Chen's sweater. Margaret looked through it.
"It does!" she announced. "It has plus signs, but only on the side that rubbed the balloon."
"Let's find out!" said Elvira. She held the magnifying glass close to Chen's sweater. Margaret looked through it.
"It does!" she announced. "It has plus signs, but only on the side that rubbed the balloon."
Then all the kids had to have a turn looking at the minus signs on
the balloon and the plus signs on the sweater. When everyone had
seen them, Chen said, "I still don't see what all these plus and
minus signs have to do with the balloons sticking to the sweaters."
"Yes," said Margaret, "and why don't the balloons stick to each other?"
"It's very simple," said Elvira.
"Yes," said Margaret, "and why don't the balloons stick to each other?"
"It's very simple," said Elvira.
Elvira doesn't tell the children what the positive and negative charges have to do with balloons sticking to sweaters. Let's keep reading to find out.
All the children wanted to use the magnifying glass to see the charges.
It must be fun to use a special magnifying glass to see charges.
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Chapter 6
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"But when you guys rubbed those balloons on your sweaters, you separated the charges. You gave a little extra negative charge to the balloons and the same amount of positive charge to the sweaters. Then, when you brought the balloons close to the sweaters, the negative charges attracted the positive ones and the balloons stuck to the sweaters."
"I got that part," said Margaret, "but if charges attract the way you say, then why do my balloons repel each other?"
"Take a look at those balloons through the magnifying glass," said Elvira. "What do you see?"
Margaret put the magnifying glass close to one of the balloons. "I see little minus signs on this one," she said. She grabbed the other balloon. "And there are minus signs on this one, too. They’re both negative."
"Aha!" said Elvira, "See, that explains it!"
"Explains what?" asked Chen. "I don’t get this!"
Margaret observes that there are minus signs on both balloons.
What does Margaret's observation help you to understand?
Margaret notices that two balloons both have negative charges on them, and they repel or push away from each other.
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"When the charges are the same kind, they repel!" said Margaret. "All the balloons are negative in this experiment, so they're all going to push away from each other."
Elvira held her hand up high and talked to the rest of the children. "Margaret just made a prediction based on her theory," she told them. "She thinks that all the balloons will repel each other, not just these two. What do you think? How will you find out?"
Everyone ran around gathering up balloons, rubbing them on their sweaters, and then trying to stick them to each other. All the balloons repelled each other.
"I've got a prediction, too!" said Chen. "The sweaters in our
experiment all have the same charge, too. All the balloons are
negative and all the sweaters are positive. The sweaters should
repel each other, too."
They tried it. The sweaters were heavier than the balloons and they didn't float around, so it was harder to see what was happening. But Tommy saved the day. He had brought a wool scarf to the party. The scarf was lighter than the sweaters and when the children rubbed the two ends with a balloon, they pushed on each other just the way the balloons had. When the children looked through Elvira's magnifying glass, the scarf had little plus signs on it, just like the sweaters.
"We've proved that positive charges repel each other, too," Chen announced proudly.
They tried it. The sweaters were heavier than the balloons and they didn't float around, so it was harder to see what was happening. But Tommy saved the day. He had brought a wool scarf to the party. The scarf was lighter than the sweaters and when the children rubbed the two ends with a balloon, they pushed on each other just the way the balloons had. When the children looked through Elvira's magnifying glass, the scarf had little plus signs on it, just like the sweaters.
"We've proved that positive charges repel each other, too," Chen announced proudly.
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Chapter 7
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Chen's parents and Elvira were cleaning up. Chen was helping.
Margaret had left, and she said she had a great time.
"That was the best party ever!" said Chen.
"I'm glad you enjoyed it," said his mother. "What part did you like best? The presents, the games?"
"I'm guessing the cake!" said his father.
"No," said Chen, smiling up at Elvira, "It was the balloons."
The End
Congratulations! You have completed this activity. Click on the Home button below, then ask your teacher for further instructions.
"That was the best party ever!" said Chen.
"I'm glad you enjoyed it," said his mother. "What part did you like best? The presents, the games?"
"I'm guessing the cake!" said his father.
"No," said Chen, smiling up at Elvira, "It was the balloons."
Congratulations! You have completed this activity. Click on the Home button below, then ask your teacher for further instructions.
Now that we are at the end, it's a great time to summarize the story.
Think about the major events of the story. In Chen's words, the balloons were the best part of the party. Why?
During a birthday party, the children learned about electrical charges by separating charges on balloons and seeing them with a special magnifying glass.
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Electrical birthday party
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In this activity you will explore how to combine positive and negative numbers. |
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Engage
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"But -6 is lower down on the number line than -3," Margaret pointed out. "The negative sign reverses everything. So -6 is smaller than -3!"
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A +1 and a –1 can be removed because together they add up to zero. They cancel each other out. One could call this the canceling rule.
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You have a rule for
adding
positive and negative
numbers, which is to
add
a positive or negative square
to the number line. To
subtract
a positive or negative
number,
remove
the right number of squares.
You can also add a positive along with a negative square without changing the amount. |
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Explain
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and negative
electric charges on an object are equal, the charge adds up to 0 and
the object is electrically neutral.
Elaborate
Congratulations! You have completed this activity.
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What are positive and negative numbers?
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In this activity, you will use a computer model to build a circuit that will light two holiday lights with a battery. |
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Engage
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Imagine that you have one holiday light and a battery. How
would you connect them to light up the bulb?
Use the drawing tool to make a circuit. You can use the battery stamp 
and the light stamp
.Use the pencil to draw wires.
Take a snapshot when you think your circuit will work. This snapshot will be saved in your lab book. |
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Explore
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Have you ever used a computer model to build something?
You will use a computer model to focus on the different parts needed to make a bulb light up.
By using a model of electrical equipment, you can experiment safely. Think about each part and the way you connect them.
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You will be able to drag two wires, a battery, and a light
bulb into the blue workspace.
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You can connect the pieces any way you want. Drag the ends
(junctions) together to connect them.
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Disconnect the ends by right-clicking on the junction and
choosing "split junction."
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This model was created using a
PhET
model.
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This sounds like a fun challenge!
You need to make a circuit that lights the bulb with the battery.
With the model, you can easily try many combinations of bulb, wires,
and battery. Pay attention to what you change each time until you
succeed!
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This model was created using a PhET model.
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Try another challenge to learn more about circuits.
What do you notice? Did you try the same steps as before?
Use the same strategy as before with two bulbs. Or try a different
strategy.
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Explain
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There are two ways to connect light bulbs in a circuit.
In series means "one after the other." Here is a diagram of light bulbs in series. Notice how the charges flow through first one, and then the other bulb, along the same path. |
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- If one light is removed from a series circuit, the other one won't work.
- If one light is removed from a parallel circuit, the other one will still work.
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Elaborate
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This model was created using a
PhET
model.
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Make one a parallel circuit.
Make the other a series circuit.
- If one light is removed from a series circuit, the other one won't work.
- If one light is removed from a parallel circuit, the other one will still work.
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Congratulations! You have completed this activity. |
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How do you design a circuit that will light up several bulbs?
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In this activity, you will measure the temperature of a holiday light. |
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Engage
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Suppose you could measure all of the light and heat energy
coming out of a regular incandescent bulb.
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Explore
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The fast response temperature sensor has a tiny tip that
measures temperature. Put the tip against the holiday light
and hold it in place with a small piece of clear tape.
Get ready to connect the two leads of the light to the two ends of the battery, but don't do it yet. |
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Use the label tool
on the right.
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for
a technical hint.
for
a movie showing how to use the data collection graph.
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| Slide the tip of the temperature probe in between the bulb and the aluminum foil. |
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for
a technical hint.
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Explain
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Elaborate
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Choose the "two" dataset. Start recording temperature. Let it run for ten seconds.
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Congratulations! You have completed this activity. Click on the Home button below, then ask your teacher for further instructions.
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What kinds of energy does a bulb produce?
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This activity uses hand generators and capacitors to make and store electricity. |
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Engage
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Explore
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| Attach the Genecon to a holiday light. Light it up by cranking. Don't go too fast – you may burn out the bulb! |
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| Join up with another team so that you have two Genecons. See if you can run one Genecon with another. |
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| A capacitor is a special device that stores electric charges. You can picture it as two plates that aren't connected, with extra positive charges on one side and negative charges on the other. When the two sides are connected in a circuit, the charges flow. |
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The capacitor looks like this. The plates are hidden inside it.
You can charge up a capacitor with the Genecon! |
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| Connect the Genecon to the capacitor. |
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Compare your results with other groups in the class.
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Connect the holiday light across the capacitor. Keep it
connected for at least 10 seconds. Watch the light bulb.
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Compare your result with other groups in the class.
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Explain
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Elaborate
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Connect the voltage sensor to the computer. Click on the magnifying glass
for
a technical hint.
Click on the magnifying glass
for
a movie showing how to use the data collection graph.
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In the draw tool, put the number where each of these things
happens:
Take a snapshot of your drawing. |
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- Chemical energy is stored.
- Electrical energy is transported.
- Light energy is produced.
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Heat energy is produced.
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Congratulations! You have completed this activity.
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How can you make and store electricity?
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What is electricity?
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1
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Now it's time to review and summarize what you have learned
about electricity. To help, you can show all of your snapshots
and some of your written answers from the activities. They are
all in your lab book.
Review the questions on the following pages. There is a separate page for each of the activities that you worked on. Be prepared to share your answers with the rest of the class. |
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Electrical birthday
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Charged balloons
In this activity, you placed charges on balloons and watched what
they did.
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Light it up!
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Light and heat
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Crank up the lights
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Plus and minus
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Summary
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Let your teacher know that you are done. Your teacher will give you a password so you can take a short test.
| Password: |
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Wrapping up
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1. Here are two circuits, each with one battery and two light
bulbs. Answer the questions about these two circuits.
| A |
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B |
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Press the Right Arrow below to go to the next page.
Press the Right Arrow below to go to the next page.
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Press the Right Arrow below to go to the next page. |
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Press the Right Arrow below to go to the next page.
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| Click the Submit button when you have finished. |
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What have you learned about electricity?
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