Under point charges understand the body, withelectric charge, linear dimensions of which can be ignored. The distance between them can be measured directly measured with a ruler, calipers or a micrometer.

But to do it is practically very difficult.

Therefore, you can use Coulomb's law.

You will need

• - Sensitive dinamometr-
• - kalkulyator-
• - Table permittivity materials.

instructions

1

Connect the charge known to the leverssensitive dynamometer. Use torsional dynamometer which measures the force depending on the rotation of the wire, which is suspended from one of the bodies. When placing avoid charges of touch, or the quantity of electric charge redistributed, the force of interaction will change, and the measurement is not correct.

2

In the measurement of the force of interaction necessarilyobserve the polarity of the charge, since like charges repel and opposite charges attract each other. Therefore, the scale can be rotated in different directions. In determining the distance between the opposite charges, let them touch.

3

Measure the strength of the interaction of charges in Newton. To determine the distance between the two charges r, find the product of modulus values ​​of these charges q1 and q2, multiply the resulting number by a factor of 9 • 10 ^ 9, divide by the result of power module, dynamometer measured F. From the resulting extract the square root of the result r =? (( 9 • 10 ^ 9 • q1 • q2) / F). The results are obtained in meters.

4

If the reaction is carried out not in chargevacuum or air, consider the dielectric constant of the medium, where the interaction occurs. Find its value in a special thematic table. For example, if you are charging in kerosene, then keep in mind that its dielectric constant of? = 2. Permittivity of free space and air is? = 2.

5

In calculating the distance between the charges thatare in substance, the dielectric constant of which is different from 1, before taking the square root of the result of calculation to divide the distance between the two charges on the dielectric constant?. In this case, the formula for calculating the distance between two point charges has the form r =? ((9 • 10 ^ 9 • q1 • q2) /? • F).