Question

Define electric current. What is its SI unit?

Answer 1

Hint: We will use the relationship between electric charge and electric current to form the definition of electric current. Electric current is directly proportional to electric charge and inversely proportional to the time passed. The SI unit of charge is coulomb and SI unit of time is seconds

Complete step by step answer:
The flow of electric charges produces an electric current. If there is a net amount of charge Q which is flowing across a cross sectional area in time t, then the electric current is given by the formula below:
\[I = \dfrac{Q}{t}\] ,
Where \[I\]is the electric current through the cross sectional area.
Thus the amount of charge flowing per unit time across any cross sectional area of a conductor held perpendicular to the direction of the flow of charge is defined as an electric current\[I\].
In metallic conductors, current is due to the motion of negatively charged particles, that is the electrons. In electrolytes, current is due to the motion of positive and negative ions moving in opposite directions. While in semiconductors, partly the electrons and partly the holes are responsible for the transmission of electric current.
Since the charge is measured in coulombs and time in seconds, so the unit of electric current is coulomb/Sec or ampere (A). The ampere is the SI unit of the conductor. Thus, a wire is said to carry a current of one ampere when a charge at the rate of one coulomb per second is flowing through it.
Conventional Direction of Flow of Current: As per the electron theory, when there is a potential difference applied across a conductor, then some matter flows through the circuit which produces the electric current. It was at that time considered that this matter flows from higher potential to lower potential, that is, from the positive terminal to the negative terminal of the cell through the external circuit. This convention of flow of current is so firmly established that still we are using it. Thus, the conventional direction of flow of current is considered flowing from the positive terminal of the cell towards the negative terminal of the cell throughout the external circuit.
On the basis of the flow of electric charge the current is mainly classified into two types, which are alternating current and direct current. In direct current, the charges flow through is in a single direction whereas in alternating current the charge flows in both the directions.

So, the correct answer is “Option A”.

Note:
Current can also be defined through Ohm's law. In Ohm’s law, 1 ampere current is produced when there is a battery producing 1 volt of voltage along a circuit, when a resistor is connected to the circuit having an internal resistance of 1 ohm. According to the Ohm’s law, \[I = \dfrac{V}{R}\].
In electrolytes, current is due to the motion of positive and negative ions moving in opposite directions.