Physics MCQs set 2 for PAF Officer GDP / GD (Initial Test) Everyday Science — 20 solved questions.
Q1. One kilowatt-hour is the amount of electrical energy that is consumed by a 1000-watt appliance in:
Answer: 1 hour
Explanation: One kilowatt-hour equals the energy consumed by a 1000-watt (1 kW) device operating for exactly 1 hour; by definition, Power × Time = 1 kW × 1 h = 1 kWh.
Q2. Which among the following types of lenses are prescribed by doctors for a patient suffering from astigmatism?
Answer: Cylindrical lens
Explanation: Astigmatism results from an irregularly shaped cornea or lens; cylindrical (toric) lenses compensate by refracting light differently in different meridians to correct the uneven curvature.
Q3. Which instrument is used to measure the power of an electric circuit?
Answer: Wattmeter
Explanation: Wattmeter is the scientifically accurate choice. The concept tested here is core everyday science for MDCAT, ECAT, and general ability papers.
Q4. Which of the following gases is used in cigarette lighters?
Answer: Butane
Explanation: Butane (C₄H₁₀) is the fuel used in most disposable and refillable cigarette lighters because it is easily liquefied under moderate pressure and vaporizes readily at room temperature.
Q5. A loudspeaker changes ______ energy into sound energy.
Answer: Electrical
Explanation: A loudspeaker converts electrical energy (alternating current signals) into mechanical vibrations of a cone/diaphragm, which then produce sound waves in the surrounding air.
Q6. Television signals are converted into light signals for transmission through:
Answer: Optical fiber
Explanation: Optical fibre cables transmit data as pulses of light (converted from electrical signals), enabling high-speed, long-distance telecommunication with minimal signal loss.
Q7. The lightest metal is:
Answer: Lithium
Explanation: Lithium is the lightest metal with a density of only 0.534 g/cm³ and atomic mass 6.941; it is so light it can float on water.
Q8. What is the SI unit of Charge?
Answer: Coulomb
Explanation: The SI unit of electric charge is the Coulomb (C), defined as the charge transported by a current of one ampere in one second (1 C = 1 A·s).
Q9. The cosmic microwave background radiation comes from:
Answer: The Big Bang
Explanation: The cosmic microwave background (CMB) radiation is the thermal afterglow of the Big Bang, released about 380,000 years after the event when the universe cooled enough for atoms to form.
Q10. Which of the following devices is used to step up or step down the voltage of an alternating current?
Answer: Transformer
Explanation: A transformer uses electromagnetic induction to increase (step up) or decrease (step down) the voltage of an alternating current, based on the ratio of turns in its primary and secondary coils.
Q11. Which of the following is Right for sound?
Answer: Sound cannot travel through a vacuum
Explanation: Sound is a mechanical wave that requires a physical medium to travel; it cannot propagate through a vacuum because there are no particles to transmit the compressions and rarefactions.
Q12. Two parallel wires carrying currents in the same direction attract each other because of:
Answer: Magnetic forces between them
Explanation: Parallel wires carrying currents in the same direction create magnetic fields that interact - by the right-hand rule and Ampere's force law, the magnetic force between them is attractive.
Q13. The velocity of wind is measured by an:
Answer: Anemometer
Explanation: An anemometer measures wind speed and direction; it typically consists of rotating cups whose speed of rotation is proportional to wind velocity.
Q14. The study of energy production in living bodies is called:
Answer: Bioenergetics
Explanation: Bioenergetics is the branch of biology that studies how living organisms transform, store, and use energy through metabolic processes such as cellular respiration and photosynthesis.
Q15. The kilowatt-hour is a unit of:
Answer: Energy
Explanation: The kilowatt-hour (kWh) is a unit of energy equal to 3.6 × 10⁶ joules, representing the work done by a 1-kilowatt device operating for one hour.
Q16. Light waves can be polarized because they:
Answer: Are transverse waves
Explanation: Polarization is possible only in transverse waves, where oscillations are perpendicular to the direction of propagation; light is a transverse electromagnetic wave, so it can be polarized.
Q17. Which of the following substances is the lightest?
Answer: Hydrogen
Explanation: Hydrogen is the lightest substance (element) with an atomic mass of approximately 1 u and density of 0.0000899 g/cm³ at STP, making it the least dense element in the universe.
Q18. The newton-meter is a unit of:
Answer: Work
Explanation: A newton-meter (N·m) is the SI unit of work and energy (equivalent to a Joule), representing the work done when a force of one newton acts over a displacement of one meter.
Q19. For sending sound waves over large distances, which waves are used?
Answer: Radio waves
Explanation: Radio waves are used to carry sound signals over long distances because they can travel through the atmosphere and space, be modulated with audio information, and be received by antennas.
Q20. Ultraviolet light is visible, but infrared light is not visible.
Answer: Wrong
Explanation: Both ultraviolet and infrared light are invisible to the human eye; the human visible spectrum is roughly 380-700 nm, so UV (below 380 nm) and IR (above 700 nm) are both outside visible range.