ELECTRIC FORCE AND ELECTRIC CHARGE
Ordinary matter consists of atoms. Each atom consists of a nucleus, consisting of protons and neutrons, surrounded by a number of electrons. The masses of the electrons, protons and neutrons are listed in Table 1. Most of the mass of the atom is due to the mass of the nucleus.
|Table 1: Masses and charges of the building blocks of atoms. |
The diameter of the nucleus is between 10-15 and 10-14 m. The electrons are contained in a roughly spherical region with a diameter of about 2 x 10-10 m. Measurements of the velocity of the orbital electrons in an atom have shown that the attractive force between the electrons and the nucleus is significantly stronger than the gravitational force between these two objects.
Electric Force (Fc) and Electric Charge:
“The attractive force between the electrons and the nucleus is called the electric force”. Electric force between two objects is proportional to the inverse square of the distance between the two objects. The electric force between two electrons is the same as the electric force between two protons when they are placed at the same distance. This implies that the electric force does not depend on the mass of the particle. Instead, it depends on a new quantity is called electric charge. The unit of electric charge q is the Coulomb (C). The electric charge can be negative, zero, or positive. The electric charge on a glass rod rubbed with silk is positive.
• there are two kinds of charge, positive and negative
• like charges repel, unlike charges attract
• positive charge comes from having more protons than electrons; negative charge comes from having more electrons than...