What is meant by electric current? Name and define S.I unit. In a conductor electrons are flowing from B to A. What is the direction of conventional current? Give justification for your answer.

Electric current refers to the flow of electric charge in a circuit. In most practical cases, it involves the movement of electrons through a conductor. The flow of electrons constitutes an electric current.

S.I. Unit:
The SI (International System of Units) unit of electric current is the ampere, symbolized by the letter 'A.' One ampere is defined as one coulomb of charge passing through a conductor in one second. Mathematically, it is represented as:

1 A = 1 C/s (coulomb per second)

Direction of Conventional Current:
The direction of conventional current is the opposite of the actual flow of electrons in a circuit. Conventionally, the direction of current flow is considered from positive to negative, which is opposite to the direction of the electron flow.

Justification:
The convention for the direction of conventional current was established before the discovery of the electron and the understanding of its behavior in a circuit. When scientists first started studying electricity, they were unaware of the existence of electrons and their role in current flow.

The direction of conventional current was defined based on observations and practical reasons. Electric current was initially thought to be the flow of a positive charge carrier, which was later discovered to be incorrect. However, this convention was already well-established and is still used today for consistency and historical reasons.

When electrons flow from point B to point A in a conductor, the conventional current is considered to flow from point A to point B in the opposite direction. This convention is widely adopted and is essential for understanding circuit diagrams, analyzing circuit behavior, and expressing electrical quantities consistently in various electrical engineering applications.