Why does the electrometer needle deviate from the vertical position if some charge is imparted to the metal rod?

When a charged body touches the rod of the electrometer, the charges are distributed along the conductors – the arrow and the rod. Repulsive forces act between the electric charges of the same name on the rod and arrow, which cause the arrow to turn. The greater the electric charge is imparted to the electrometer, the greater the angle the arrow is deflected.

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