On Thursday, I'll be at the science fair with Mike, Nick, and our new hand cranked Van de Graaff generator. Mike was asked to think of something to demonstrate to the kids that night. The woman who was organizing the science fair thought of Mike from the science he did with the Cub Scouts. One night, he lit up a pickle like a fluorescent light to demonstrate electricity. Another time, he hung each of the boys from a block and tackle to show them how a pulley worked. Then, he showed them how they could blow through a straw contraption that they built to hold a ping pong ball up in midair, demonstrating Bernoulli's Principle, the very concept that keeps an airplane in the air. The boys loved it. So when it came to the science fair, Mike was a natural.
I asked him a couple of weeks ago what he thought he'd do. He's usually very quiet about these projects so I didn't expect to hear an answer.
"I'm going to build a Van de Graaff generator," he said, grinning. "You know, the ball you put your hand on to see your hair fly up."
Oh, now that is very cool!
Last week, a big box arrived in the mail and the next thing I knew, Mike had assembled a large table-top generator. It was very pretty, but I wondered if one of us would be electrocuted. I was also curious about how much it cost him, so I asked.
"Oh, it was $200," he said casually. Wow! Mike really goes all out. "But you know, we'll use it," he added. Oh, I don't care. I just think he's funny, the way he likes his toys. I began to imagine all the classrooms that we could visit, letting Nick run experiments as if he were a magician. Last year, Nick performed the pickle experiment for the kids in his class. They loved it. We could visit my friend, Marian, who teaches fifth grade. We could visit classrooms in Nick's school. This thing could be passed from one Cub Scout den to another. In my head, each time we use it, we lower the cost of it, in a sense. The first hour we spent playing with it cost us $200 per hour. Then today, we added some experiments I found online. After another hour of showing the boys what we could do, it lowered the cost to $100 per hour. After two hours at the science fair, we'll be at $50 per hour and it goes down from there. Already, it doesn't seem that expensive compared to what the kids are learning. Shoot, I'm even learning some things.
Here's what you can do with a Van de Graaff generator. You can put a person on a footstool and ask her to put her hand on the aluminum ball then turn the crank. Her hair will stand on end, each filament trying to stay as far as possible from the other. You can actually see if your hairstylist has cut your hair evenly. This experiment takes some courage, but the worst that can happen is that you get a static shock, like kissing the cat on a dry winter day. I looked it up to make sure.
The Van de Graaff we bought can generate up to 50,000 Volts. That sounds like a lot, but the current output is only about 50 micro Amps. I learned that current kills, but voltage just makes your hair stand on end. An AA alkaline battery only delivers 1.5 Volts with 0.700 Amps. Now, you should know that power, or Watts, comes from multiplying the current with the voltage. The value of the power tells you how much it's going to hurt if you get zapped. Touching both terminals of that battery with your tongue would be about the same as the zap you'd get from our generator if your feet were on the ground. We will have to be careful with cell phones and pacemakers though.
Nick asked if we were making lightning. That's a good question. An average bolt of lightning delivers 10,000,000 Volts carrying 30,000 Amps. Static discharges are a little like lightning in that they both have voltage, current, and snappy lines of light in the air. The difference is that static discharge has a tiny bit of current that zaps you like when your husband walks around in his socks in the winter and then kisses you, but lightning has enough current to melt sand into glass. I don't want to be the one standing on that beach when the lightning hits.
I remembered the analogy about voltage and current being like a waterfall. The height of the waterfall shows the voltage and the amount of water going over shows the current. So the static electricity of our Van de Graaff generator is like a tall and very narrow waterfall, not so powerful. Lightning is like a tall and very wide waterfall. It could knock your socks off, literally.
With a Van de Graaff generator, you can perform feats of levitation with aluminum pie plates. All I had to do was balance them on the sphere and crank it up. They levitated for a second then flew away one by one like Frisbees. The negative particles on the sphere got onto the the pie plates and then repelled each other which caused the levitation. It's a little like the way you can make one magnet fly away from another by trying to push both negative ends together. Cool!
You can make a piece of paper hang from the sphere, but you can also make hole punches or confetti or even Rice Krispies dance and then scatter all over the floor. You could zap the cat, but that would be mean. Our cat, Buddy, has a hard enough time with his fly-away fur when it's cold and dry. He hates getting zapped while I'm petting him, so I think I'll keep him far away when we're cranking out the electrons.
Thank you for listening, jb
I asked him a couple of weeks ago what he thought he'd do. He's usually very quiet about these projects so I didn't expect to hear an answer.
"I'm going to build a Van de Graaff generator," he said, grinning. "You know, the ball you put your hand on to see your hair fly up."
Oh, now that is very cool!
Last week, a big box arrived in the mail and the next thing I knew, Mike had assembled a large table-top generator. It was very pretty, but I wondered if one of us would be electrocuted. I was also curious about how much it cost him, so I asked.
"Oh, it was $200," he said casually. Wow! Mike really goes all out. "But you know, we'll use it," he added. Oh, I don't care. I just think he's funny, the way he likes his toys. I began to imagine all the classrooms that we could visit, letting Nick run experiments as if he were a magician. Last year, Nick performed the pickle experiment for the kids in his class. They loved it. We could visit my friend, Marian, who teaches fifth grade. We could visit classrooms in Nick's school. This thing could be passed from one Cub Scout den to another. In my head, each time we use it, we lower the cost of it, in a sense. The first hour we spent playing with it cost us $200 per hour. Then today, we added some experiments I found online. After another hour of showing the boys what we could do, it lowered the cost to $100 per hour. After two hours at the science fair, we'll be at $50 per hour and it goes down from there. Already, it doesn't seem that expensive compared to what the kids are learning. Shoot, I'm even learning some things.
Here's what you can do with a Van de Graaff generator. You can put a person on a footstool and ask her to put her hand on the aluminum ball then turn the crank. Her hair will stand on end, each filament trying to stay as far as possible from the other. You can actually see if your hairstylist has cut your hair evenly. This experiment takes some courage, but the worst that can happen is that you get a static shock, like kissing the cat on a dry winter day. I looked it up to make sure.
The Van de Graaff we bought can generate up to 50,000 Volts. That sounds like a lot, but the current output is only about 50 micro Amps. I learned that current kills, but voltage just makes your hair stand on end. An AA alkaline battery only delivers 1.5 Volts with 0.700 Amps. Now, you should know that power, or Watts, comes from multiplying the current with the voltage. The value of the power tells you how much it's going to hurt if you get zapped. Touching both terminals of that battery with your tongue would be about the same as the zap you'd get from our generator if your feet were on the ground. We will have to be careful with cell phones and pacemakers though.
Nick asked if we were making lightning. That's a good question. An average bolt of lightning delivers 10,000,000 Volts carrying 30,000 Amps. Static discharges are a little like lightning in that they both have voltage, current, and snappy lines of light in the air. The difference is that static discharge has a tiny bit of current that zaps you like when your husband walks around in his socks in the winter and then kisses you, but lightning has enough current to melt sand into glass. I don't want to be the one standing on that beach when the lightning hits.
I remembered the analogy about voltage and current being like a waterfall. The height of the waterfall shows the voltage and the amount of water going over shows the current. So the static electricity of our Van de Graaff generator is like a tall and very narrow waterfall, not so powerful. Lightning is like a tall and very wide waterfall. It could knock your socks off, literally.
With a Van de Graaff generator, you can perform feats of levitation with aluminum pie plates. All I had to do was balance them on the sphere and crank it up. They levitated for a second then flew away one by one like Frisbees. The negative particles on the sphere got onto the the pie plates and then repelled each other which caused the levitation. It's a little like the way you can make one magnet fly away from another by trying to push both negative ends together. Cool!
You can make a piece of paper hang from the sphere, but you can also make hole punches or confetti or even Rice Krispies dance and then scatter all over the floor. You could zap the cat, but that would be mean. Our cat, Buddy, has a hard enough time with his fly-away fur when it's cold and dry. He hates getting zapped while I'm petting him, so I think I'll keep him far away when we're cranking out the electrons.
Thank you for listening, jb
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