Types of electricity

Common types of electricity are static electricity, direct current (DC) electricity and alternating current (AC) electricity.

Static electricity is the collection of free electrons on the surface of a material, giving it a negative (−) charge. Atoms on the surface of another material that have lost one more of their electrons are called positive (+) ions. 4____ Static electricity is caused by rubbing the two different materials together. Since opposite charges attract, there is a tendency for the electrons to attract toward the positive ions, resulting in static electricity.

In a metal or other conducting material, electrons will flow from an area of an excess negative (−) charges to an area of positive (+) charges. 5____ If the opposite charges are constant, such as with the terminals in a battery, the current is called direct current or DC electricity, because it is going in one direction. If the terminals constantly switch their polarity from (+) to (−) and back again, the direction of the electrons alternates and is call alternating current or AC electricity. 6 ____

DC can be created by a battery or DC generator. AC requires an AC generator for its creation. DC is used in many devices that do not require high voltages for their operation, such that batteries are used for power. AC can be used in higher voltages. 7 ____ AC is required for many electronic devices.

Language study

Task 3

Read the extract. Underline the subject and the predicate of the sentences in bold type.

Task 4

What part of speech are these words in the given extract - nouns or verbs?

Put N for a noun and V for a verb:

flows , heats , glows , link , lights , sets , discharge , force , decrease , act .

Everyday modern life is pervaded by electromagnetic phenomena. When a light bulb is switched on, a current flows through a thin filament in the bulb; the current heats the filament to such a high temperature that it glows, illuminating its surroundings. Electric clocks and connections link simple devices of this kind into complex systems such as traffic lights that are timed and synchronized with the speed of traffic. Radio and television sets receive information carried by electromagnetic waves traveling through space at the speed of light. To start an automobile, currents in an electric starter motor generate magnetic fields that rotate the motor shaft and drive engine pistons to compress an explosive mixture of gasoline and air; the spark initiating the combustion is an electric discharge, which makes up a momentary current flow.

Many of these devices and phenomena are complex, but they derive from the same fundamental laws of electromagnetism. One of the most important of these is Coulomb’s law, which describes the electric force between charged objects. Formulated by the 18th-century French physicist Charles-Augustin de Coulomb, it is analogous to Newton’s law for the gravitational force. Both gravitational and electric forces decrease with the square of the distance between the objects, and both forces act along a line between them.

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