Objective 1

At the vertices of a rectangle with sides a = 30 cm and b = 40 cm are identical point charges q = 1 SCLC. Find the electric field at a point outside the rectangle on its axis of symmetry at a distance a = 30 cm from the middle of the long side.

Given:

Task 2

In the infinite uniformly charged surface of the thread is allocated in the form of coaxial cylinder radius, the axis of which coincides with the thread. The length of the cylinder L. Feed the electric field vector of the thread through the surface of the cylinder is equal to $ 0. Find the potential difference between the points of the field, and lying at a distance from the cylinder axis.

Objective 3

Find the capacitance of a spherical radius of the conductor surrounded by a spherical dielectric layer with an inner radius and an outer radius, dielectric constant of the dielectric.