The principle of a pressure cooker is MCQ with Answer and Explanation

Explanation:
Work done to stretch spring from 0 to x: W₁ = ½kx². Work done from 0 to 2x: W₂ = ½k(2x)² = 2kx². Thus work for additional stretch from x to 2x: ΔW = W₂ - W₁ = 2kx² - ½kx² = ³/₂kx². Spring force is variable (F=kx), so work is integral of F·dx, yielding parabolic energy storage. Memory aid: Elastic potential energy U = ½kx²; always calculate difference for incremental work. This problem tests understanding of work done by variable forces, a common theme in energy conservation questions in competitive exams.

Explanation:
While Faraday performed the groundbreaking experimental work discovering electromagnetic induction, it was James Clerk Maxwell who formalized these discoveries mathematically. Maxwell's equations (a set of four differential equations) elegantly united electricity, magnetism, and optics, proving theoretically that light itself is a propagating electromagnetic wave.

Explanation:
Electromagnetic waves are transverse: electric field (E) and magnetic field (B) are perpendicular to each other and both perpendicular to the direction of wave propagation. This is a fundamental property derived from Maxwell's equations. Memory tip: 'EM waves: E ⊥ B ⊥ propagation direction; right-hand rule for orientation'. This conceptual question tests electromagnetic wave fundamentals, crucial for modern physics in competitive exams. Always recall that EM waves require no medium and travel at speed of light in vacuum.