Two identical non-conducting solid spheres of equal mass and charge hang in air from a common point on two non-conducting massless strings of equal length. At equilibrium the strings make an angle alpha between them. The spheres are then submerged in a dielectric liquid of density 800 kg/m

Question

Two identical non-conducting solid spheres of equal mass and charge hang in air from a common point on two non-conducting massless strings of equal length. At equilibrium the strings make an angle alpha between them. The spheres are then submerged in a dielectric liquid of density 800 kg/m³ and dielectric constant 21. If the angle between the strings stays the same after immersion, then:

Accepted Answer

The electric force between the spheres decreases.. Immersion in the dielectric reduces the electric force by a factor K = 21, so the force decreases (option B correct). Keeping alpha fixed requires Fₑ/W_eff constant; this gives rho/(rho - 800) = 21, yielding rho = 840 kg/m³ (option C also correct). The classic JEE answer accepts both B and C; the single best/most direct statement is that the electric force reduces.

Solution

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