Current vs Charge
Current and charge are two concepts involving the electric properties of matter. A thorough understanding of the concepts of charge and current is highly important in fields such as physics, electrical engineering, electronic engineering, mechanics and communication technologies. These concepts are very useful in understanding electromagnetic field theory, which is a very important field in physics. In this article, we are going to discuss in depth what charge and current are, their definitions, useful calculations involving them, their similarities, what causes charge and current and their differences.
Charge
Charge is a basic scientific concept, which cannot be exactly defined. It is sometimes defined as a property of matter, which causes the matter to experience a force when other charges are at a finite distance. This definition itself holds charge, which means, this is not a complete definition. However, the behaviors of charges are well studied and thoroughly modeled. There are two types of charges, positive charges and negative charges. Charges placed at a finite distance from each other always exert forces on each other. This force was first defined using a model of action at a distance. Due to the incompleteness of this model, physicists later defined it using the electromagnetic field. Charge is said to create an electric field around it. The strength of this electric field for a point charge is given by E = Q/4πεr2, where Q is the charge in coulombs, ε is the electric permittivity of the medium, and r is the distance to the point at which the strength is measured from the charge. The unit for measuring charge is coulomb, which is named in honor of Charles-Augustin de Coulomb. The electric field lines are also a concept involved in charges. They are an imaginary set of lines, which starts at a positive charge point and ends at a negative charge point. Charge is a conserved property of the universe. It is also a relativistic invariant, which means the charge of an object does not change with greater speeds.
Current
Current is defined as the rate of flow of charges through a medium. These charges are usually in the form of electrons. The SI unit for current is ampere, which is named in honor of Andre-Marie Ampere. Current is measured using ammeters. 1 Ampere is equal to 1 Coulombs per second. An electromotive force is required for a current flow. If the voltage difference between two points is zero, there can be no net current between the two points. Current also exist in the forms such as surface current and eddy current. A current or any moving charge always produces a magnetic field apart from the electric field. This magnetic field is normal to the velocity of charge and the electric field.
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What is the difference between current and charge? ¤ Charge is a vaguely defined concept, while current is a well-defined concept. ¤ Current is the flow of charges, stationary charges cannot give any current. ¤ Charge gives rise only to an electric field, while current produces both electric and magnetic fields.
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