Electrical Engineering ⇒ Topic : Electrically charged particles

ELECTRICALLY CHARGED PARTICLES

When an electric field is applied to a conducting medium, such as a length of copper wire, electrons in the outer orbits of the copper atoms are forced out of their orbits and they travel along the wire. The direction of the movement of electrons is determined by the direction of the electric force. The protons do not move because they are very heavy. A proton of hydrogen (the lightest element) is about 1836 times heavier than an electron. Therefore, only the electrons which are lighter, move under the influence of the electric force. When an electron is removed from the orbit of an atom, it becomes a free electron. Electrons of certain metallic atoms are very loosely bound to the nucleus and they can be removed to form free electrons even with the use of a very small amount of force.It is these free electrons that constitute the flow of electric current in electrical conductors.

When an atom is hit by an electron or by another atom, its internal energy increases. Then, the atom is said to be excited. When the excess energy of an excited atom is large, it can make the loosely bound outer electrons to leave the atom. An atom that has thus lost or gained one or more electrons is said to be ionised. If an atom loses an electron, it becomes positively charged and is called a positive ion. On the other hand, if an atom gains an electron, it becomes negatively charge, and is called a negative ion. Free electrons, positive ions and negative ions, all are electrically charged particles.