However, when the negatively charged balloon is brought near the paper, the balloon repels the electrons in the paper to the far side of the paper, leaving the side near the balloon slightly positive. The attractive force between the negative charges on the balloon and the positive charges on the upper surface of the paper causes the paper to move toward and stick to the balloon. In this case the electrons are attracted to the glass and move to the top surface of the paper.
This phenomenon is called charging by induction. Another useful tool for detecting static charge is an electroscope Fig. When a negatively charged object is brought near the metal end of the scope Fig. When a positively charged object is brought near the electroscope Fig. The stronger the charge, the greater the separation of the leaves.
The triboelectric series will help you select materials from your electrostatics kit that generate a strong charge on an object. The electroscope will allow you to detect a charge. Now the electroscope will allow you to identify whether an object is positively or negatively charged.
If you bring a negative object near the electroscope, the electrons in the scope will be repelled toward the leaves, balancing the charge. The leaves will move toward each other.
If you bring a positive object near the electroscope, it will attract the electrons toward the terminal. The leaves will move away from each other. You can also use this process with a positive object to charge the electroscope. In this case, grounding the electroscope with your finger will allow extra electrons to move to the electroscope, which will become negatively charged. Static electricity is an interesting phenomenon, and that's probably all many of us think about it—it's interesting but not very useful.
However, we know that without current electricity to power our homes and run our computers and cell phones, our lives would be very different.
The electric technologies we rely on every day couldn't have been built without some early scientist taking an interest in static electricity. Static electricity can be beneficial or damaging. Some smoke stacks use electrostatic devices called scrubbers to help remove particulates from the smoke. Static electricity can damage the circuitry in some electronic devices. Therefore, parts for a computer might be shipped in special packaging to prevent damage from static electricity.
What other uses have scientists found for static electricity? Can you come up with an experiment to develop your own triboelectric series? We use cookies to provide you with a great user experience. By using our site, you accept our use of cookies.
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Succession on Mount St. Interdisciplinary Teach a class like forensic science where you have to apply physics, chemistry, and biology content? The foil is on the left side of the conducting rod. There is no net charge on this electroscope. This is a content, but boring, electroscope. Let's mix things up a little. We rub our rubber rod, making it negative, bring it close, and The foil is moving! It's magic! The foil is moving because the foil and the conducting rod next to it are both negatively charged.
How do I know this? I'm smart, that's why. When the negatively-charged rod is brought close to the electroscope, positive charges are attracted to it and negative charges are repelled away from it.
Since protons do not move they comprise the structure of all things , the negatively-charged electrons are the only charged particles within the electroscope that can move in response to this charged rod. As the rubber rod is brought near, electrons are pushed down into the electroscope, negatively charging the conducting rod and foil, leaving the top part positively charged. Note that the net charge of the electroscope is still zero. If I take the rod away at this point:.
If, now, we bring the negatively-charged rubber rod in contact with the top part of the electroscope so that charge may transfer between the electroscope and the rubber rod, this will not be the case. The electroscope has a net neutral charge and the rubber rod has a net negative charge. If they are brought into contact, they will both take a net negative charge. Take away the rubber rod and the electroscope is left with a negative charge. Bring back the negatively-charged rod and even more electrons get shoved down into the electroscope.
Charge up a glass rod with silk giving it a positive charge and bring it close and the surplus of electrons concentrates more heavily toward the top, neutralizing the lower part a bit.
The positive tape is attracted to the nearby negative charges more strongly than it is repelled by the more distant positive charges, and the tape moves toward your hand. Note that charge leaks slowly off the tape into the air or along the surface of the tape, so you may have to recharge your tape after a few minutes of use.
You can use your electroscope to test whether an object is electrically charged. First, use the comb to determine the charge on a piece of tape, and then see whether an object with an unknown charge repels the tape. If the tape is negatively charged and an object repels it, then the object is negatively charged. If tape is attracted to an object, the tape and the object may have opposite charges, or the tape may be charged and the object uncharged, or the object may be charged and the tape uncharged.
But if the tape is repelled by the object, the tape and the object must have the same charge. The only way that tape and an object will neither repel nor attract is if both are uncharged. Charge a tape, and hang it from a straw. Charge a comb by running it through your hair or rubbing it with wool. Bring the charged comb near the charged tape, and watch the tape move. Wiggle the comb side-to-side near the tape, and watch the tape wiggle side-to-side.
Scientists model this interaction by saying that the comb creates an electric field that moves across space and exerts a force on the charges on the tape.
When you wiggle the comb side-to-side, the electric field radiating from the comb also oscillates side to side. The oscillations of the electric field create magnetic oscillations, which, when combined, are also known as electromagnetic waves. These waves travel outward at the speed of light and will cross space even through a vacuum. Attribution: Exploratorium Teacher Institute. Connect with us! Get at-home activities and learning tools delivered straight to your inbox.
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