What is electric charge and how is it measured?

Electric charge is a fundamental property of matter that determines its electromagnetic interactions and is measured in coulombs.

Electric charge is a basic property of electrons, protons and other subatomic particles. It is this property that causes them to experience a force when placed in an electromagnetic field. There are two types of electric charges: positive and negative. Like charges repel each other, while unlike charges attract each other. This is the principle that governs the interactions of particles at the atomic and molecular levels, and is responsible for the structure and behaviour of all matter.

The unit of electric charge in the International System of Units (SI) is the coulomb, symbolised by 'C'. One coulomb is equivalent to the charge of approximately 6.242 x 10^18 electrons or protons. This is a very large amount of charge, so in practice, charges are often measured in smaller units like the microcoulomb (µC) or nanocoulomb (nC).

The amount of electric charge can be measured using an instrument called an electrometer. This device measures the force between two charged objects and uses this to calculate the amount of charge. Alternatively, the charge can be determined indirectly by measuring the current flowing in a circuit over a known period of time, since current is simply the rate of flow of charge.

In summary, electric charge is a fundamental property of matter, responsible for the electromagnetic interactions between particles. It is measured in units of coulombs, using instruments like the electrometer or by measuring electric current.