Charge is the flow of ______?

CONCEPT:

Electric current:

• The flow of electric charges through a conductor constitutes an electric current.
• Quantitatively, electric current in a conductor across an area held perpendicular to the direction of flow of charge is defined as the amount of charge flowing across that area per unit time i.e.,

\({\rm{Electric\;curernt\;}}\left( {\rm{I}} \right) = \frac{{{\rm{Electric\;charge}}\;\left( {\rm{Q}} \right)}}{{{\rm{Time\;}}\left( {\rm{t}} \right)}}\)

• SI unit of current is ampere and it is denoted by the letter A.

EXPLANATION:

• In solids valence electrons freely move throughout the conductor, i.e., valence electrons are not attached to the atoms.
• When an electric field is applied, these valence electrons start flowing in a particular direction constituting the electric current. Therefore option 3 is correct. 

Important Points 

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• As the charge may be flowing in different directions at a particular time and space, so we consider the net flow of charge, i.e,         

\({\rm{Electric\;curernt\;}}\left( {\rm{I}} \right) = \frac{{{\rm{Total \, Electric\;charge}}\;\left( {\rm{Q}} \right)}}{{{\rm{Time\;}}\left( {\rm{t}} \right)}}\)                       

• ����ℎ��������������������If q+ is the positive charge flowing and if q- is the negative charge flowing, the net charge q = q+ - q-
•  In case charge flowing through an area varies with time, i.e., for non-steady current, we have

\(Electric \,\,current (I)=\frac{dq}{dt}\)

Additional Information 

• Valence electrons move opposite to the direction of current flow. 
• The direction of current flow is in the direction of the electric field.
• Current carriers in liquids- positively and negatively charged ion.
• Current carriers in gasses- positive ions and electrons.