The device used to increase or decrease AC voltage is MCQ with Answer and Explanation

Explanation:
KE ∝ p² (since KE = p²/(2m)). If KE increases by 300%, new KE = 4× original KE. Thus p_new² / p_original² = 4 ⇒ p_new / p_original = 2 ⇒ momentum doubles, i.e., 100% increase. Memory tip: 'KE ∝ p²; so %Δp = ½ %ΔKE for small changes, but for large changes use ratio'. This proportional reasoning problem tests energy-momentum relationship, frequently appearing in competitive exams. Always derive from fundamental relations when percentages are large; linear approximations fail here.

Explanation:
K = p²/(2m) => 100 = 2500/(2m) => m = 2500/200 = 12.5 kg.

Explanation:
According to Einstein's photoelectric equation, the kinetic energy of emitted electrons depends exclusively on the frequency of the incident light and the metal's work function. Intensity represents the number of photons striking the surface per second. More photons mean more collisions with electrons, leading strictly to an increase in the number of emitted photoelectrons (photoelectric current), not their energy.