Question

In which direction does current flow in an electric circuit? Also, write the SI unit of electric current.

Answer 1

Hint:Electric circuit is an arrangement of several conducting wires, connected to different electrical devices like a battery, an ammeter, a voltmeter. Electric current is nothing but a uniform flow of electrons.

Complete answer:
Conductivity is an innate property of certain materials. These materials have high values for conductivity$\left( \sigma \right)$ and low values of resistivity$\left( \rho \right)$. The reason behind these values is the presence of free charge carriers. These charge carriers can be anything. In aqueous solutions of electrolytes, these charge carriers are ions; whereas in semiconductors these charge carriers are holes left in the materials because of excitation of electrons.

In case of conductors, these charge carriers are free electrons present in the material. Most of the conductors are solid metals. In solids the structure in which its atoms are placed is known as its lattice. These electrons move from one atom to another randomly in the lattice.Now since electrons are negatively charged entities, they tend to move towards the positive charge.

But in a neutral conductor, where there is no positive and no negative, and it is not connected to any battery of any sorts, these electrons move randomly around the lattice, producing zero net displacement. But when the conductor is connected to both the terminals of a battery, some changes occur.

A battery acts as a source of electromotive force, which is a force required for uniform motion of electrons. What a battery does is it applies an external electric field inside the conductor. The direction of this electric field is from the positive terminal of battery to the negative terminal of battery.

But since electrons are attracted to positive charge, the electrons move in the direction opposite to the electric field, which is from the negative terminal to the positive terminal of the battery. Since electric current is a uniform flow of electrons, its direction is opposite to the flow of electrons.

Therefore the direction of electric current in an electric circuit is from the positive terminal to the negative terminal of the battery. Its SI unit is ampere$\left( A \right)$.

Note:The functioning of electric current is analogous to the mechanics of free fall. In a free fall, the object moves from a position with higher gravitational potential to a position with lower gravitational potential. And the force responsible for creation of this gravitational position gradient is the Gravitational Force. Similarly, electric current moves from a position with higher electrical potential to a position with lower electrical potential. And the force responsible for the creation of electrical potential gradients is Electromotive Force.