SLECTION OF GAUSSIAN SURFACE

STATEMENT -1 : If ointvec(E).bar(ds) over a closed surface is negative,it means the surface encloses a net negative charge. STATEMENT-2 : We may have a Gaussian surface in which three lines enter and five field lines are coming out. STATEMENT-3 : The quantity ointvec(E).bar(ds) is independent of the charge distribution inside the surface.

Selection Of Gaussian Surface

A Gaussian surface encloses a proton p. The electric field at any point on the surface is vec€ . The flux linked with the Gaussian surface is phi . STATEMENT-1 : When an electron is kept close to this system outside the Gaussian surface, the flux linked with the surface would change. and STATEMENT-2 : The presence of electron will alterthe electric field on the gaussian surface.

Refer to the arrangement of charges in Fig and a Gaussian surface of radius R with Q at the centre. Then

Consider a Gaussian spherical surface covering a dipole of charge q and -q, then

A+q_(1) charge is at centre of an imaginary spherical Gaussion surface 'S', and -q_(1) charge is placed nearby this +q_(1) charge inside 'S'. A charge +q_(2) is located outside this Gaussian surface. Then electric field on Gaussian surface will be :

Gauss's law and Coulomb's law , although expressed in different forms , are equivalent ways of describing the relation between charge and electric field in static conditions . Gauss's law is epsilon_(0) phi = q_(encl) ,when q(encl) is the net charge inside an imaginary closed surface called Gaussian surface. The two equations hold only when the net charge is in vaccum or air . If the charge q_(3) and q_(4) are displaced (always remaining outside the Gaussian surface), then consider the following two statements : A : Electric field at each point on the Gaussian surface will remain same . B : The value of oint vec(E ) .d vec(A) for the Gaussian surface will remain same.

Assertion: Four point charges q_(1),q_(2),q_(3) and q_(4) are as shown in Fig,The flux over the shown Gaussians surface depends only on charges q_(1) and q_(2) Reason:Electric field at all points on Gaussians surface depends on any charges q_(1) and q_(2)