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Static electricity

Electrical charges

All matter is made up of atoms. Atoms consist three types of particles: protons, neutrons and electrons.

There are two types of electric charges: positive and negative.

  • Electrons have negative charge.

  • Protons have positive charge.

In this chapter you will learn:

  1. What are electric charges?

  2. What is static electricity?

  3. What is electric field?

  4. What are field lines?

Generally, the atom has equal number of electrons and protons; therefore, it has neutral charge. However, if there is a loss of electrons, the atom becomes positively charged. On the other hand, if there is a gain of electrons in the atom, it becomes negatively charged.

Charged atoms are called ions.

Static electricity

Static electricity is the result of an imbalance between negative and positive charges in an object. Static electricity is all about electric charge that cannot move as a normal electric current in a conducting material.

Static electricity generally forms in insulating materials like plastics, styrofoam, paper, rubber and glass. Static charge is produced when two insulating surfaces are rubbed together. When insulating materials rub against each other, they experience friction between them. This force of friction causes electrons to gain enough energy to leave one material and get transferred to the other. Such transfer of electrons causes imbalance of charges in both the materials. The material that gained electrons becomes negatively charged, while the other material that lost electrons becomes positively charged.

Note: When static electricity is formed, only electrons move; the positive charges do not move. Positive charge exists because the material has lost electrons.

Note: Too much accumulation of static charge results in a high potential difference, which can cause sparks.

Electric fields

An electric field is created around any object that is electrically charged. When an electrically charged object is placed in the electric field of another object, it will experience a non-contact force of static electricity.

Electric fields around charged particles are shown as diagrams with arrows (field lines). The following are important points about electric fields and how they are represented in a diagram using field lines:

  • Field lines point in the direction in which a positive charge will be moved due to the electrostatic force. These lines (arrows) go from positive to negative.

  • They are at a right angles to the surface of the charged object.

  • The closer the field lines are, the stronger the electric field.

  • The strength of electric field decreases as the distance from the charge increases. This means the electrostatic force also decreases with the increase in distance.

Sparks occur when there is a big enough potential difference between an electrically charged object and the earth.

Air is a good electrical insulator, but when it is ionised it is more conductive, so an electrical current can flow. This is called spark.

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