Question

The SI unit of electric flux is
A.)\[{N}/{C}\;\]
B.)\[{Nm}/{C}\;\]
C.)\[N{{m}^{2}}\]
D.)\[{N{{m}^{2}}}/{C}\;\]

Answer 1

Hint: The electric flux can be defined as the number of electric field lines passing through a given area. Therefore, the units of electric flux are related to units of electric field and cross-sectional area as the product of the units of these two quantities.

Complete step by step answer
We are familiar with the word field, charge etc. Charge is a property associated with the mass. With the help of the charge, we are able to produce and experience fields like electric field and magnetic field. Thus charges are solely responsible for the electric field.

Electric field of a charge is a region around which we can experience the force exerted by the charge. When we bring any charged object into the field of another charge, it will experience a force. It may be a force of attraction or a force of repulsion.

Field lines are imaginary lines which give the direction of the electric force at a particular point. They are vectors which have both magnitude and direction. We can draw it around the empty space in the electric field.

The direction of the electric force at a particular point is given by drawing a tangent to that point. Charges are of two types – positive and negative charges. The electric field lines of a positive charge are always directing out wards where as that of negative charge, always shows inward direction. The two field lines will never intersect. If they intersect that implies that at that point there are two directions of electric force. This is not acceptable.
Electric flux is the number of field lines passing through a given surface. Or it is the rate of flow of electric field through a given area. Its equation is

\[\Phi =EA\cos \theta \]…………(1)
Where E is the electric field intensity = \[\dfrac{F}{q}\]
             A is the area through the electric field lines are passing
             \[\theta \] is the angle between field lines and the normal to the surface.
Thus the unit of electric flux will be \[\dfrac{N}{C}{{m}^{2}}\]. Or in simple form , it is \[{N{{m}^{2}}}/{C}\;\]

Thus option D is the answer.

Note: electric flux doesn’t depend on the shape of the surface. Field lines always start from positive charge and end at negative charge. When \[\theta ={{0}^{0}}\Rightarrow \Phi =EA\] is the maximum flux.