11. Practice Questions for Revision
Free study material · concepts, shortcuts & solved questions
The following short-answer style questions mirror the pattern commonly seen in SSC and Railway General Science papers. Attempt each one before checking the explanation, and use them as a final self-check after completing this chapter.
Q1. Which instrument is used to measure atmospheric pressure, and who invented it?
Answer: The barometer, invented by Evangelista Torricelli, is used to measure atmospheric pressure.
Q2. An ammeter is always connected in ______ with the circuit, while a voltmeter is connected in ______.
Answer: An ammeter is connected in series; a voltmeter is connected in parallel.
Q3. Which instrument works on the principle of Hooke's Law?
Answer: The spring balance, which measures weight/force based on the proportional extension of a spring under load.
Q4. Name the instrument used to measure the depth of the sea.
Answer: The fathometer (echo sounder), which uses echo-ranging with ultrasonic sound waves.
Q5. Which instrument is used to record the electrical activity of the heart?
Answer: The electrocardiograph (ECG/EKG), pioneered by Willem Einthoven.
Q6. What does a hygrometer measure, and how does it differ from a hydrometer?
Answer: A hygrometer measures humidity (moisture in air); a hydrometer measures the relative density of a liquid using flotation. They are commonly confused due to similar names.
Q7. Which optical instrument uses two parallel mirrors set at 45° to view objects out of the direct line of sight?
Answer: The periscope, commonly used in submarines.
Q8. Which instrument measures the rotational speed of an engine in RPM?
Answer: The tachometer.
Q9. A screw gauge has a higher precision than a vernier callipers. State the typical least count of each.
Answer: Vernier callipers: about 0.01 cm (0.1 mm). Screw gauge: about 0.001 cm, roughly ten times finer.
Q10. Which instrument is based on the principle of conservation of angular momentum and is used in inertial navigation systems?
Answer: The gyroscope.
Q11. Name the instrument used to test hearing sensitivity across different sound frequencies.
Answer: The audiometer.
Q12. Distinguish between radar and sonar in terms of the wave used and the medium of use.
Answer: Radar uses radio waves and is mainly used in air/space for detecting aircraft and weather; sonar uses sound waves and is used underwater for depth-sounding and detecting submarines.
Q13. Which instrument would a doctor use to examine the interior of a patient's eye?
Answer: The ophthalmoscope.
Q14. What is the working principle of a pyrometer, and why can it measure temperatures a normal thermometer cannot?
Answer: A pyrometer measures the intensity of radiation emitted by a hot body without requiring physical contact, allowing it to measure very high temperatures (such as inside a furnace) that would destroy a contact-based liquid thermometer.
Q15. Which instrument is used by navigators to measure the angle of a celestial body above the horizon?
Answer: The sextant.
Q16. Name the instrument that combines an ammeter-like current coil and a voltmeter-like pressure coil to measure electric power.
Answer: The wattmeter.
Q17. Which two instruments both work on an 'echo' principle but use different types of waves, one in water and one in air/space?
Answer: Sonar/fathometer (sound waves, underwater) and radar (radio waves, air/space) — lidar (laser light) is a third such instrument, used for precision 3-D mapping.
Q18. What quantity does a viscometer measure, and give one industry that commonly uses it.
Answer: A viscometer measures the viscosity (resistance to flow) of a fluid; it is commonly used in the petroleum and paint industries.
Q19. Which instrument is used to compare or accurately measure EMF without drawing current from the source?
Answer: The potentiometer, using the null-deflection (balance point) method.
Q20. Name the medical instrument, invented by René Laennec, used to listen to heart and lung sounds.
Answer: The stethoscope.
Q21. Which instrument measures the relative density of milk, and what is this specific instrument called?
Answer: A hydrometer measures relative density of liquids in general; the specialised version used for milk is called a lactometer.
Q22. State the principle on which a manometer works, and how it differs from a barometer.
Answer: A manometer measures the pressure of an enclosed gas/fluid using the height difference of a liquid column in a U-tube; unlike a barometer, it does not measure the open atmosphere but the pressure within a closed vessel or pipe.
Q23. Which instrument is used to measure the concentration of sugar in fruit juice using the bending of light?
Answer: The refractometer, which measures refractive index via the critical angle of total internal reflection.
Q24. Name the instrument used to record brain-wave activity, and state one condition it helps diagnose.
Answer: The electroencephalograph (EEG); it helps diagnose epilepsy, among other neurological conditions.
Q25. Which instrument is essentially a resonance box with a stretched wire, used to study the laws of vibrating strings?
Answer: The sonometer.
Q26. What is the key difference in resistance between an ideal ammeter and an ideal voltmeter, and why?
Answer: An ideal ammeter has zero resistance so it does not reduce the current it measures; an ideal voltmeter has infinite resistance so it draws no current and does not disturb the voltage it measures.
Q27. Name the scale on which earthquake magnitude is commonly reported, and the scientist associated with it.
Answer: The Richter scale, developed by Charles Richter.
Q28. Which instrument uses laser light pulses, rather than radio waves or sound waves, to measure distance and create 3-D maps?
Answer: Lidar (Light Detection and Ranging).
Q29. Distinguish between a simple microscope and a compound microscope in terms of the number of lenses used.
Answer: A simple microscope uses a single convex lens; a compound microscope uses two lens systems — an objective lens and an eyepiece — arranged to achieve much higher magnification.
Q30. Which instrument, developed by John Harrison, solved the historical problem of determining longitude at sea?
Answer: The marine chronometer.