Two point charges $a$ & $b$ whose magnitudes are same are positioned at a certain distance from each other; $a$ is at origin. Graph is drawn between electric field strength $E$ and distance x from $a$. $E$ is taken positive if it is along the line joining from $a$ to $b$

From the graph it can be decided that.

A circular disc of radius $4\mathrm{cm}$ with charge density $10 \mathrm{nC}/{\mathrm{m}}^2$ is placed in $Y-Z$ plane with center at $z=0$. Find electric field at a distance of $3\mathrm{cm}$ perpendicular to plane of disc.

Assertion: When the electric flux through a closed surface is zero then the net charge inside the surface must be zero.

Reason: When the net charge inside a closed surface is zero then electric field at every point of the Gaussian surface must be zero.

Assertion: Electric potential energy of any positive charge is always positive.

Reason: Potential energy is a vector quantity.

Assertion: In electrostatics, electric lines of force can never be closed loops.

Reason: The number of electric lines of force originating from or terminating on a charge 'is proportional to the magnitude of charge.

Assertion: If a proton and an electron are placed in the same uniform electric field they experience accelerations of different magnitudes.

Reason: Electric force on a charge is independent of its mass.

Assertion: When a charge is placed at a corner of a square, the flux passing through the square will be zero.

Reason: When electric field and area vector are perpendicular to each other at every point, then the flux passing through that surface will be zero.