The device used for detecting and measuring small electric current is MCQ with Answer and Explanation

Explanation:
Naphthalene (mothballs), camphor, dry ice sublime (solid → gas). Ice melts. Iron solid till melting. Water evaporates from liquid. Sublimation skips liquid phase.

Explanation:
High resistivity for heat, high melting point to withstand temperature.

Explanation:
F ∝ m₁m₂. Initial: 1×1 = 1. New masses 2 and 2, product 4, so force = 4F. Distance unchanged. Universal gravitation F = Gm₁m₂/r².