LED works on the principle of MCQ with Answer and Explanation

Explanation:
Newton is a derived unit representing force, defined as kg·m/s². Kelvin (temperature), Ampere (current), and Mole (amount of substance) are fundamental SI units. Derived units are combinations of fundamental units through physical relationships. Newton comes from Newton's second law: F = ma. Memory aid: Remember the seven fundamental SI units: meter, kilogram, second, ampere, kelvin, mole, candela. All others like newton, joule, watt are derived. This distinction is essential for unit conversion questions in competitive exams.

Explanation:
Magnetic force does no work, speed constant, so KE constant. Path circular.

Explanation:
U ∝ V². If V' = 2V, U' = 4U. Energy scales with square of voltage. Memory aid: 'Capacitor energy: U ∝ V²; double voltage ⇒ quadruple energy'. Electrostatics proportionality frequently tested in competitive exams.