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About "Ask A Scientist!"
On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.
Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.
A big part of understanding xerography has to do with what's called electrical charge.
There are two types of electrical charges, positive and negative. The important thing to know is that two objects that have opposite electrical charges on them (one is positive and the other is negative) will want to attract one another. This is what happens when you rub a balloon against your shirt and then stick it on the wall.
In a copier machine there is a special type of film called a photoreceptor that acts like the wall with the balloon stuck to it.
This photoreceptor is very special because if it gets charged up you can "erase" the charge by shining light on it (that's what photoreceptor means - receiver of light).
You will soon see why this is very important. When you press the button on a copier machine, several steps using electrical charges follow. First, electricity passes through a thin wire which is held just above the photoreceptor. This electricity causes the air to form lots of positive charges that are sprayed onto the photoreceptor.
Next, a beam of light, such as that from a laser is used to "write" on the photoreceptor. Remember, wherever light hits the photoreceptor the charge is erased. Where this beam writes depends on what the original sheet of paper you placed into the copier looks like, for example what numbers or words are on it.
The light beam will write on the photoreceptor where the numbers and letters are not supposed to be, causing the charge to be erased there. Where the bean doesn't hit the photoreceptor, the charges remain giving a pattern that looks just like letters and numbers on your papers.
A black or colored powder called toner is shaken over the photoreceptor. The toner particles are like balloons that stick to the wall. The toner has a negative charge and therefore sticks to positive charges that were left on the photoreceptor.
Next, a piece of paper is pressed against the photoreceptor to make the toner transfer to the paper. Finally, the paper is heated to make the toner melt into the paper so it won't rub off.
Out comes your copy. So, next time you stick a balloon to the wall, remember that electrical charges can be used to do some really useful things!
- What is the history of coding?
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- What is nanotechnology?
- How does RADAR work?
- What are computers going to look like in the future?
- How does the CCD work in a digital camera?