Electric current

What is an electrical charge? Definition, units, and types

What is an electrical charge? Definition, units, and types

An electrical charge is a physical property that determines the ability of bodies to be a source of electric and magnetic fields. These particles can interact with each other generating repulsion and attraction forces due to the electromagnetic field that they generate. Positive charges attract negative charges.

The SI unit of electric charge is the Coulomb: an electric charge that passes through the cross-section of an electrical conductor with a current of 1 ampere for 1 second.

The electric charge of a body is an invariably relativistic property. It does not depend on the frame of reference, which does not depend on whether this charge is moving or resting.

The law of conservation of charge states that the amount of electric charge in an isolated system is neither created nor destroyed.

Electrical phenomena are phenomena involving electric charges. The two sciences that study these phenomena in physics are:

  • Electrostatics explores the effect of point charges at rest.

  • Electrodynamics examines the impact of electric charges in motion.

What is an electrical charge? Definition, units, and types

Types of electrical charges

There are two types of charges:

  • Positively charged protons. Objects with a positive charge have a more significant number of protons than electrons. Protons have a positive electric charge.

  • Negatively charged electrons. Elements with a negative charge have a more significant number of electrons than protons. Electrons have a negative electric charge.

The objects without any charge have equal numbers of electrons and protons.

Protons and electrons are the two slightest electrical charges that have been observed separately. Including neutrons (which have no charge), they are the sub-particles of which the atom is composed.

What is an elementary electric charge?

An elementary charge is the minor electric charge that can exist in nature. This value of an elementary charge “e” corresponds to the charge of a proton or an electron having a value of 1.60217653 × 10 -19 C. For this reason, the electric charge only occurs in integer multiples of the elementary charge “e.”

Charges that are not multiples of “e” only occur on quarks. These are elementary particles, the charge of which is a multiple of e / 3. However, quarks have never been observed separately.

The electron

The electron is a subatomic particle with a mass of 9.10938356 × 10 -31 kg, equal to about 1/1836 that of the proton.

Within an atom, electrons appear to be moving around the nucleus.

The proton

Together with the neutron, the proton is part of the nucleus of atoms. The atomic number ( Z ) from which the chemical elements are classified in the periodic table indicates the number of protons that an atom possesses.

The proton is stable by itself. However, a free proton tends to associate with an electron and become neutral hydrogen.

What is static electricity?

When two bodies come into close physical contact, there is a possibility of transfer of free electrons between them. One gives electrons to the other, which makes it quite attractive. The energy consumed reappears in the form of an increase in electrical voltage between the two surfaces.

Static electricity is a phenomenon of surfaces generated when two or more bodies come into contact and separate again—this action results in a separation or transfer of negative electrons from one atom to another.

The level of charge (the strength of the field) depends on several factors: the material and its physical and electrical properties, temperature, humidity, pressure, and the rate of separation.

The phenomenon of static electricity can manifest itself almost anywhere and at any time. It occurs when charges have accumulated in an object and are dissipated towards another that has a lower charge, with which it comes into contact.

In a factory, in the office, at home, when shaking someone's hand, touching a doorknob, brushing against a surface, a spark suddenly jumps, causing a startle in people. But fortunately, static electricity is not always such a harmless thing.

Coulomb’s law: Electrostatic forces

The low of electric charges - or Coulomb's law - expresses the attraction or repulsion of charged objects at rest. Charges of the same sign repel each other by electrical forces, and those of opposite signs attract each other. Electrical charges can cause:

  • An electric field, regardless of its state of motion.

  • A magnetic field, if they move, they form an electric current. This is because a magnetic field exerts a Lorentz force on a charge across the direction of the field. This is the cause of the phenomenon of induction, described by Faraday's law.

Voltage and capacity of electrical charges

The repulsive force between two electric charges decreases with the square of the distance between the particles. Therefore, adding charged particles to an electrical conductor reduces the distance between the particles. Therefore, more energy is needed to add an additional charge. It is the electrical potential or voltage of the conductor, expressed in volts (V).

Electrical capacitors are used to store energy. These elements use the attractive force between oppositely charged particles on two nearby conductors to offset the repulsive force of equally charged particles within each conductor.

The charge can also be stored in a metal sphere isolated from the ground. The maximum amount of charge on electrically charged spheres depends linearly on the size of that sphere.

Publication Date: August 30, 2019
Last Revision: March 10, 2022