Point charges are understood as bodies havingElectric charge, the linear dimensions of which can be neglected. The distance between them can be measured by measuring directly with a ruler, caliper or micrometer.
But it is very difficult to do this.
Therefore, you can use Coulomb's law.
You will need
- - sensitive dynamometer-
- - calculator-
- - table of dielectric permittivity of substances.
Attach the known charges to the leversSensitive dynamometer. Use a torsional dynamometer, which measures the force, depending on the rotation of the wire on which one of the bodies is suspended. When placing charges, avoid from touch, otherwise the value of the electric charge will be redistributed, the interaction force will change, and the measurement will not be correct.
When measuring the interaction forceTake into account the polarity of the charges, since like charges are repelled, and unlike charges attract. Therefore, the balance can rotate in different directions. When determining the distance between unlike charges, prevent them from coming into contact.
Measure the interaction force of charges in Newtons. To determine the distance between two charges r, find the product of the moduli of the values of these charges q1 and q2, multiply the resulting number by a coefficient of 9 • 10 ^ 9, divide the result by the modulus of the force measured by the dynamometer F. From the result, extract the square root r =? (( 9 • 10 ^ 9 • q1 • q2) / F). The result will be in meters.
If the interaction of charges is not carried out inVacuum or air, take into account the permittivity of the medium where the interaction takes place. Find its meaning in a special thematic table. For example, if the charges are in kerosene, then consider that its dielectric constant? = 2. The dielectric constant of vacuum and air is? = 2.
When calculating the distance between charges, whichAre in a substance whose dielectric constant differs from 1, divide the result of the calculation for the distance between two charges by the dielectric constant before extracting the square root. In this case, the formula for calculating the distance between two point charges takes the form r =? ((9 • 10 ^ 9 • q1 • q2)? • F).