The SI unit of electric current is Ampere. One Ampere is defined as:

CONCEPT:

• Electric current: The flow of charge in a conductor under a potential difference maintained between the ends of the conductor constitutes an 'electric current' in the conductor. In other words, The rate of flow of charge is called 'electric current.

Thus, if in an electric circuit, an amount of charge Q flows in t second then the electric current (I) in the circuit is given by:

I = Q/t

• The SI unit of electric current is 'ampere'  (A) Ampere is a fundamental unit in the S.I system. The ampere is defined on the basis of the force acting between two current-carrying, parallel conductors.

EXPLANATION:

If Charge (Q) = 1 coulomb (C) , t = 1 second (s) ,  then i = 1 ampere (A) , thus

1 ampere = 1 coulomb / second

1A = 1 Cs^-1

Hence option 2 is correct.

Additional Information

• We know that in metals the electric current is the flow of electrons. 1 electron carries 1.6 ×  10^-19 C of charge. Hence for 1 C of charge, 1/ (1.6 × 10^-19) = 6.25 × 10¹⁸ electrons should flow in 1 second.
• Thus 1 ampere = 6.25 × 10¹⁸ electrons per second.