A. The trapped steam adds extra heat directly to the food.
B. Increased pressure raises the boiling point of water.
C. The metal of the cooker conducts heat much faster.
D. Increased pressure lowers the boiling point of water.
Answer: Option B
Solution (By JKSSB Mock Tests)
In an open vessel, water boils at 100°C, and extra heat merely creates steam rather than raising the temperature. A pressure cooker traps steam, increasing the internal pressure above atmospheric pressure. Increased pressure raises the boiling point of water (often to around 120°C). Cooking the food at this higher temperature significantly reduces cooking time.
Explanation:
SONAR (Sound Navigation and Ranging) uses ultrasonic waves (frequency > 20 kHz) because they have high directionality, short wavelength for better resolution, and minimal absorption in water. Radio waves attenuate rapidly in water; infrasonic waves have long wavelengths unsuitable for detection; light doesn't propagate far in water. Memory tip: 'Ultra = beyond human hearing; used in SONAR/ultrasound imaging'. This application question tests knowledge of wave frequency ranges and their practical uses, common in competitive exams linking physics to technology. Always recall frequency thresholds: infrasonic 20kHz.
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