The essential difference between AC and DC is MCQ with Answer and Explanation

Explanation:
Resonance: X_L = X_C ⇒ they cancel ⇒ Z = R (minimum). Current maximum at resonance. Memory tip: 'Series resonance: Z_min = R; parallel: Z_max'. AC circuit concept frequently tested in competitive exams.

Explanation:
Power P = V²/R => R = V²/P = 200²/100 = 40000/100 = 400 Ω. Also current I = P/V = 0.5 A, R = V/I = 200/0.5 = 400 Ω. Use P = V²/R for direct calculation.

Explanation:
The Doppler Effect is the apparent change in the frequency (and thus pitch) of a wave due to the relative motion between the source and the observer. As the ambulance approaches, sound waves get compressed, increasing the perceived frequency (higher pitch). As it moves away, waves stretch, lowering the frequency.