Задача 30068.

A porcelain rod 1 cm long with small metal balls fixed at the ends is placed in a uniform horizontal electric field of 2 V/m. The stick can rotate around a vertical axis passing through its middle. When the balls were given equal in value but opposite in sign charges of 10 nC each, the stick took a position of stable equilibrium. How much work must be done to rotate the rod around its axis by 180°?

A detailed solution with a brief note of the conditions, formulas and laws used in the solution, the derivation of the calculation formula and the answer.
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