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Stuck in neutral

We have already established that unlike charges attract each other, while substances with a like charge repel each other. You may also notice, however, that neutral substances, particles with no charge, become attracted to either positively or negatively charged substances.

Scatter small pieces of paper across a surface. Charge the pen by rubbing it with some cloth and then move the pen near the paper. The neutral paper will cling to the charged pen. Now repeat the experiment but move the cloth near the paper. The charged cloth will also attract the neutral paper.

Positively charged particles will attract neutral substances because the charged particles need more electrons, which they find in the neutral substance. Since the neutral substance began with a balanced number of protons and electrons, when the positively charged particles take some, the neutral substance loses electrons and becomes positive. At that point, the charges repel each other.

A similar thing happens with negatively charged particles when they try to give away their extra electrons. The neutral substance takes some extra electrons, making it negative, at which point the charges repel and the objects separate.

Induction is a term we use to describe the stimulation of a neutral object by a charged object, so when a neutral particle is made positive or negative by contact with a charged particle, it is said to have an induced charge.

Static electricity

The energy that gives objects the power of attraction and repulsion is called electrostatic force. Static means 'still' and this type of energy is 'static' because it does not move until the charged object reacts to another object. The build up of electrostatic force is called static electricity. Refer Image 1

The main difference between static electricity and other types of electricity, such as the energy currently powering your computer, is that static electricity is still or very slow-moving. As soon as electricity flows quickly from one place to another, the energy ceases to be static.

Honourable discharge

You may notice that sometimes, when you walk on carpet and then touch a bit of metal, you get a shock. Walking on carpet builds static electricity in your body. Metal is a substance that easily moves the energy, so when you touch the metal, the electricity in your body flows to the metal and you get a shock at the point of contact. If you did this in the dark, you might see a small flash of light at the same time as you feel the shock. This movement is electrical discharge. Refer animation

Discharge occurs because the electrostatic charge that you build up becomes active when it finds an object to flow to, enabling it to balance the positives and negatives. If you did not discharge the static electricity in this way, it would eventually discharge at a much slower rate, without giving you a shock.


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Question 1/5

1. Which of the following best describes particles that would be attracted to a negatively charged particle?

positive particles and neutral particles

negative particles and neutral particles

only negative particles

only neutral particles

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