Electricity Chapter 10
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A form of energy that results from the interaction of charged particles, such as electrons or protons.This can take the form of static electricity or current electricity.
Static charge (static electricity)
An electric charge that tends to stay on the surface of an object, rather than flowing away quickly. When there is an excess or deficit of electrons there is a static charge that is negative or positive respectively.
Charging by friction
A process in which objects made from different materials rub against each other, producing a net static charge on each other.
- When objects are charged by friction one material has a stronger attraction to electrons and therefore pulls electrons from the object with a weaker attraction and this results in a negative charge, the object with a weaker hold on electrons will then have a positive charge.
- A list of materials that have been arranged according to their ability to hold on to electrons.
A material in which electrons cannot move easily from one atom to another.
Ex: rubber, wood, air, pure water, etc.
A material in which electrons can move easily between atoms, metals are excellent conductors.
Ex: copper, aluminum, gold, mercury, etc.
A material in which electrons can move fairly well between atoms.
Some non-metals, such as silicon, are semiconductors.
- An object that can supply a very large amount of electrons, or can remove a very large number of electrons from a charged
- object, thus neutralizing the object.
The Earth is a ground since it is so large and has so many charges it can give or take electrons very easily and hardly affect its net charge.
A device for detecting the presence of an electric charge.
- One type is the pith ball electroscope. It consists of a small and light ball suspended by a cotton string, when a charged object comes close to the ball the electric force between them moves the light ball; towards
- the object. Another type would be the metal leaf electroscope.
Charging by contact
Generating a charge on a neutral object by touching it with a charged object.
- When a negative object touches a neutral object electrons flow to the neutral object from the negative object making the
- formerly neutral object negative, enough electrons stay in the negative object so that it always remains negative after the transfer. The reverse happens when a positive object touches a neutral one in that electrons flow from the neutral
- object to the positive one making them both positive.
Laws of electric charges
Laws that describe how two objects interact electrically when one or both are charged.
These are the three laws of electric charges:
1. Like charges repel, so if a positive and a positive object, or a negative and a negative object meet, they will repel each other.
2. Opposite charges attract, so if a positive and a negative object meet, they will attract.
3. Charged and neutral objects attract, so if a positive and a neutral, or a negative and a neutral object meet, they will attract.
- A property of the space around a charged object, where the effect of its charge can be felt by other objects. Objects with greater net charges have stronger electric fields. Also the greater the distance from the
- charged object, the weaker the force of the electric field.
Induced charge separation
The movement of electrons in a substance, caused by the electric field of a nearby charged object, without direct contact between the substance and the object.
- For example, if you bring a negative rod near a neutral pith ball, the electrons in the pith ball will move away from the rod which
- will make the part of the pith ball closest to the rod positive and then it will be attracted to the rod.
A charged atom or group of atoms. Ions are atoms that do not have the same amount of electrons as of protons.
- This happens during a thunderstorm and causes lightning.
A metal sphere or point attached to the highest part of a building and connected to the ground.
- A thick copper wire is attached to the rod and is connected to a bare wire or metal plate in the ground so that the lightning
- strike can’t damage the building.
A type of cleaner that removes unwanted particles and liquid droplets from a flow of gas.
The electrostatic precipitator is used to remove sulfuric acid, smoke, and ash from smoke stacks used in ore smelting operations, coal-burning plants, and cement kilns. They work by inducing a strong positive charge on the particles via a positively charged wire, the particles then induce a negative charge on the collection plates, they then collide with the collection plates, get neutralized, and fall into hoppers below.
Van de Graaff generator
- A device that accumulates very large charges and can
- transfer very large charges.
- The generator works by having an insulated sphere on a column, inside the column there is a rubber belt that is driven by a motor, and finally there is a metal collecting comb on the top that collects charge on the
A small device that detects and measures exposure to radiation.
People who work with radioactive materials, equipment, or environments often need to wear one.
Some radiation dosimeters act like film and radiation darkens the film, some are like metal leaf electroscopes with their leaves apart and radiation knocks the leafs detecting the radiation.
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