The unit of power, watt, is equivalent to MCQ with Answer and Explanation

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:
Thermionic emission: electrons emitted when metal heated to high temperature (e.g., filament in cathode ray tube). Photoelectric: light incident. Field emission: strong electric field. Secondary: bombardment by particles.

Explanation:
Centripetal force acts radially inward, perpendicular to tangential displacement. Work W = F·d·cosθ; θ=90° ⇒ cos90°=0 ⇒ W=0. No energy transfer occurs; speed remains constant in uniform circular motion. Memory tip: 'Perpendicular force ⇒ zero work'. Conceptual question testing work-energy understanding, common in competitive exams to identify misconceptions about circular motion.