Beats frequency = |f₁ - f₂|. For 256 Hz and 260 Hz, beats per second: MCQ with Answer and Explanation

Explanation:
Pressure cooker seals steam, increasing internal pressure above atmospheric. Higher pressure raises water's boiling point (above 100°C), allowing food to cook at higher temperature, speeding up chemical reactions. Option A is vague; C and D are secondary effects. Memory tip: 'Higher pressure ⇒ higher boiling point ⇒ faster cooking'. This daily-life physics question tests application of pressure-temperature relationship in liquids, frequently appearing in competitive exams. Always recall that phase change temperatures depend on pressure (e.g., water boils below 100°C on mountains).

Explanation:
Watt is unit of power (J/s). Kilowatt-hour is energy (power × time). Joule is SI unit of energy. Electron volt is energy unit (1.6×10⁻¹⁹ J). Remember: power = energy/time. So watt is not energy.

Explanation:
The number of half-lives (n) that have passed is total time / half-life = 15 / 5 = 3 half-lives. The fraction of the sample remaining undecayed is given strictly by the formula (1/2)^n. Therefore, the fraction remaining is (1/2)^3 = 1/2 * 1/2 * 1/2 = 1/8.