Difference between Electric Current and Electric Charge

Electric current and Electric charge are the two most fundamental electrical quantities in any electric circuit. The major difference between current and charge is that the electric charge is the subatomic property of all the materials in nature, while the electric current is the direct flow of electric charge in an electric circuit. There are several other noticeable differences between charge and current which we are going to highlight in this article.

Let's start with some basics of electric charge and electric current so that it becomes easy to understand the differences between them.

What is Electric Charge?

Electric charge or simply charge is the property of subatomic particles of substances by virtue of which the substances exhibit the electrical behavior. It is denoted by symbol ‘Q’ or ‘q’ and is measured in coulombs (C).

Charge is the universal property of all the matter because every matter in the nature is composed minute particles called atoms. An atom, in turn, is made of three major subatomic particles - electrons, protons and neutrons.

Electrons and protons carry a certain amount charge which is equal in magnitude but having opposite polarity. Where, an electron carries a negative electric charge of 1.6 × 10-19 C, while a proton carries a positive charge of the same magnitude as that of electronic charge. Hence, we can classify the charge in two types, i.e. negative charge and positive charge.

Electric charge has different properties, where the most significant one is the nature of force acting between them. This property of electric charge states that the like charges (i.e. positivepositive and negative-negative) repel each other while the unlike charge (positive-negative) attract each other.

For the electric charges, the law of conservation charge is also established which states that the charge can neither be created nor destroyed, i.e. the total charge of a system remains constant.

Depending on the movement of charge it can be of two types namely static charge and moving charge. The static charge remains stationary on a surface as in case of electrostatics and results in the existence of electric field, on the other hand, the moving or dynamic charge is the one which moves from one point to another and results in electric field as well as magnetic field. The electric charge is the primary factor due to which the electric current flows in a circuit.

What is Electric Current?

Electric current is nothing but the directed flow of electric charge (more specifically electrons). Mathematically, the time rate of flow of electrons in a conductor is called the electric current, and it is denoted by symbol ‘i’ or ‘I’ i.e.

$$i(t)=\frac{dq(t)}{dt}$$

Where, ‘i’ is used to denote time varying current, whereas ‘I’ is used to denoted constant current. The above relation shows that the electric current is the function of electric charge in time domain. The electric current is measured in amperes (A).

Based on the relationship between magnitude of current and time, the electric current can be classified into two types namely: constant current and varying current.

• Constant current is the one whose magnitude does not change with time such as DC (Direct Current) supplied by battery.

• Varying current is the one whose magnitude changes with time as in case of pulsating DC, alternating current (AC), etc.

It is a convention to take the direction of flow of electric current from positive terminal to negative terminal. But, the actual direction of flow of current is from negative to positive, it is because the electric current is the flow of electrons that flow from negative terminal to positive terminal.

Difference between Charge and Current

The following table highlights all the key differences between electric current and electric charge

Difference between Electric Charge Electric Current
Definition Electric charge is the property of subatomic particles of matter by which it exhibits electric behavior. The rate of flow of electric charge in a specific direction is known as electric current.
Denotation Electric charge is denoted by symbols ‘Q’ or ‘q’. Electric current is denoted by symbols ‘i’ or ‘I’.
Formula

Electric charge is given by,

$$Q\:=\:ne$$

Where, n = 0, 1, 2… and e is the charge on an electron.

Electric current is given by, $$I\:=\:\frac{Q}{t}$$
SI Unit The SI unit of electric charge is Coulomb (C). The SI unit of electric current is Ampere (A).
Types Electric charge is of two types namely, positive charge and negative charge. Electric current is of two types namely, constant current and timevarying current.
Particles Electric charge is due to electrons and protons. The electron carries a negative charge, while proton carries positive charge. Electric current is due to flow of electrons.
Law of conservation The law of conservation of charge states that charge can neither be created nor destroyed. The law of conservation of current is not stated.
Effects Electric charges show the electric effect when static, and electric as well as magnetic effects when moving. Electric current shows the heating effect, magnetic effect, electric effect, etc.
Measuring instrument Electric charge is measured by using an electrometer. Electric current is measured by using an ammeter (ampere-meter).

Conclusion

From the above discussion, we can note that electric charge and current are related quantities. We observed that the current is the movement electric charge in a specific direction. Mathematically, the relation between charge and current is given by the formula of current, i.e.,

$$I\:=\:\frac{Q}{t}$$

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