The specific resistance (resistivity) of a metallic conductor depends exclusively upon its:
A. Cross-sectional area
B. Length
C. Nature of material and temperature
D. Volume
Answer: Option C
Solution (By JKSSB Mock Tests)
Resistance depends on length and area (R = rho * L / A), but specific resistance or resistivity (rho) is an intrinsic property of the material itself. It does not depend on the geometric dimensions of the conductor (length, area, volume). Resistivity strictly depends on the atomic structure (nature of the material) and the thermal vibrations (temperature of the material).
Explanation:
Newton's second law: F = ma ⇒ a = F/m = 20 N / 5 kg = 4 m/s². Direct application of fundamental dynamics equation. Memory tip: Always convert to SI units first; here already in kg and N. Basic numerical testing F=ma application, commonly appearing in competitive exams to verify formula recall and unit handling.
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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