The weight of a body is zero when it is MCQ with Answer and Explanation

Explanation:
Seven base units: metre, kilogram, second, ampere, kelvin, mole, candela. All other units derived. This is standard definition. Supplementary units radian and steradian now considered dimensionless derived units.

Explanation:
When a body is lifted against gravity, work done (mgh) is stored as gravitational potential energy. This energy can be recovered when the body falls. Kinetic energy relates to motion, thermal to heat, elastic to deformed materials. The conservation of energy principle states that work done against conservative forces becomes potential energy. Formula: PE = mgh, where h is height above reference. Memory aid: 'Potential' means stored energy due to position. This conceptual question tests energy transformation understanding, frequently appearing in work-energy theorem applications in competitive exams.

Explanation:
Fuse wire melts when current exceeds rating (Joule heating I²R), breaking circuit to prevent damage. Sacrificial overcurrent protection. Memory aid: 'Fuse = thermal cutoff; rated current slightly above normal'. Safety device function frequently tested in competitive electricity sections.