Consider an arbitrary electrostatic field configuration. A small test charge is placed at a null point (i.e., where E = 0) of the configuration. Show that the equilibrium of the test charge is necessarily unstable.

Answer carefully: A small test charge is released at rest at a point in an electrostatic field configuration. Will it travel along the field line passing through that point?

Electric field is the electrostatic force per unit charge acting on a vanishingly small test charge placed at that point. It is a vector quantity and the electric field inside a charged conductor is zero. Electric flux f is the total number of electric lines of force passing through a surface in a direction normal to the surface when the surface is placed inside the electric field The electric field at a point is

A positive charge Q is uniformly distributed along a circular ring of radius R. A small test charge q is placed at the centre of the ring.

Electric field is the electrostatic force per unit charge acting on a vanishingly small test charge placed at that point. It is a vector quantity and the electric field inside a charged conductor is zero. Electric flux f is the total number of electric lines of force passing through a surface in a direction normal to the surface when the surface is placed inside the electric field We have a Gaussian of radius R with Q at the centre then

Electric field is the electrostatic force per unit charge acting on a vanishingly small test charge placed at that point. It is a vector quantity and the electric field inside a charged conductor is zero. Electric flux phi is the total number of electric lines of force passing through a surface in a direction normal to the surface when the surface is placed inside the electric field. phi=ointvecE.vec(ds)=q/epsilon_0 A positive charge Q is uniformly distributed along the circular ring of radius R. A small test charge q is placed at the centre of te ring as shown.

Electric field is the electrostatic force per unit charge acting on a vanishingly small test charge placed at that point. It is a vector quantity and the electric field inside a charged conductor is zero. Electric flux phi is the total number of electric lines of force passing through a surface in a direction normal to the surface when the surface is placed inside the electric field. phi=ointvecE.vec(ds)=q/epsilon_0 The electric field at a point is

Electric field is the electrostatic force per unit charge acting on a vanishingly small test charge placed at that point. It is a vector quantity and the electric field inside a charged conductor is zero. Electric flux phi is the total number of electric lines of force passing through a surface in a direction normal to the surface when the surface is placed inside the electric field. phi=ointvecE.vec(ds)=q/epsilon_0 If there is only one type of charge in the universe, then

Electric field is the electrostatic force per unit charge acting on a vanishingly small test charge placed at that point. It is a vector quantity and the electric field inside a charged conductor is zero. Electric flux phi is the total number of electric lines of force passing through a surface in a direction normal to the surface when the surface is placed inside the electric field. phi=ointvecE.vec(ds)=q/epsilon_0 If ointvecE.vec(ds)=0 over a surface, then

Electric field is the electrostatic force per unit charge acting on a vanishingly small test charge placed at that point. It is a vector quantity and the electric field inside a charged conductor is zero. Electric flux phi is the total number of electric lines of force passing through a surface in a direction normal to the surface when the surface is placed inside the electric field. phi=ointvecE.vec(ds)=q/epsilon_0 We have a Gaussian surface of radius R with Q at the centre, then