LED works on the principle of MCQ with Answer and Explanation

Explanation:
When B starts, A has already traveled 10 m/s × 2 s = 20 m. Relative velocity of B w.r.t A = 15 - 10 = 5 m/s. Time to cover 20 m gap at 5 m/s relative speed = 20/5 = 4 s after B starts. Since B started 2 s late, total time from A's start = 2 + 4 = 6 s. Alternatively, equate distances: 10t = 15(t-2) ⇒ 10t = 15t - 30 ⇒ t = 6 s. This relative motion approach simplifies pursuit problems. Memory tip: In same-direction motion, use relative velocity = |v₁ - v₂|. Frequently tested in kinematics sections of competitive exams.

Explanation:
Rectifier (diode bridge) converts AC to DC. Inverter DC to AC. Transformer changes AC voltage level. Oscillator generates AC signal. Electronic devices often need DC.

Explanation:
Michael Faraday built the first electric generator (Faraday disk) in 1831, based on electromagnetic induction. Tesla contributed to AC motor and polyphase system. Edison DC systems. Watt steam engine.