**Potential** is power characteristic of electric field. To find its value, it is necessary to divide potential energy of a charge in this point of electric field into a charge. For various types of fields different formulas of calculation of potential are used.

## It is required to you

- - ruler.

## Instruction

1. If the potential energy of a charge of a body in this point of electric field (conditionally, it is work on moving of a charge to infinity) is known, then find potential, having divided this potential energy in Joules into charge size in Pendants: φ=Wp/q, where: φ - the size of required potential, Wp - potential energy of a charge of a body, q - charge size. Potential is measured in volts.

2. If electric field is formed by a dot charge, then for determination of capacity of its field in any point, find distance from this point to a charge. Then the capacity of the field will be equal in this point to the work of coefficient 9•10^9 on value of a charge divided into distance to a charge in meters: φ=9•10^9•q/r, where: r - distance to a charge.

3. When the field is formed by the sphere, consider two cases. Capacity of the field or on its surface is equal in a point which is in the sphere to the work of coefficient 9•10^9 on the sphere charge divided into its radius: φ=9•10^9•Q/R, where: Q - the charge of the sphere, R is sphere radius. This formula is applied irrespective of in what place of the sphere there is a space point.

4. If the point of space is out of the sphere, then calculate the capacity of the field as the work of coefficient 9•10^9 on value of a charge of the sphere of the space divided into distance from a point to the center of the sphere: φ=9•10^9•Q/R, in this case, R - distance from a point to the center of the sphere.

5. To determine the capacity of the field formed by other loaded surfaces by Gauss's theorem define tension of the field formed by these surfaces. After that find distance from a surface to a space point in which potential is defined. For this purpose from a point lower a perpendicular to a surface. To find potential, increase value of electric field strength in this point by the measured distance: φ = E·d, where: Е - value of electric field strength, d - distance from a surface to a point.

6. If between a source of electric field there is some substance, then all results which turn out when calculating, it is necessary to divide into value of dielectric permeability of the environment which is between a point of the field and its source.