Theory Summary
· The electric forces of bodies are described in the sense of electric charge.
· Electric forces are either attractive or repulsive. In nature there are only two types of electric charges: the positive and the negative. The same charged bodies repel each other, while the opposite ones are attracted.
· Atoms are made up of the nucleus and electrons. At the core are protons that have a positive charge. The electron has a negative charge equal to that of the proton. A positively charged body has a lack of electrons, while a negatively charged body has an excess. In an electrically neutral body, the number of protons is equal to the number of electrons.
· The bodies are electrified in three ways: friction, contact, induction. The more electrons are added or removed from a neutral body the more load we say it acquires.
· An area of space is called an electric field if electric forces are exerted on any charged body we bring into it. The electric field is described by the dynamic lines.
· Every charged particle in an electric field has dynamic energy.
Coulomb Law on forces between electrically charged bodies
The measure of the electric force (F) between two charged bodies (q1 and q2) is proportional to the product of the charges and inversely proportional to the square of the distance between them (r).
K is a ratio constant. Its value depends on the material in which the charged bodies are located and on the system of the units we use. Its value in the International System of Units for vacuum and approximately for air is:
Where q1, q2 are the electrical charges measured in C (Coulomb), r is the distance between the charges measured in meters and K is the constant as shown above.
According to Coulomb’s Law, the force F between two charges of 1 C, placed 1 meter apart is equal to 9 billion N (Newtons) which in real life is 10 times the weight of a warship.
1 C = 6.24 x 1018 electrons.