SET 10

🎯 Objectives: TOWARD NECTA Physics - Set 10 Questions and Answers

SET 10: NECTA Form Four Physics Conceptual Questions and Answers

  1. What is the principle of conservation of energy?
    Answer: Energy cannot be created or destroyed; it can only change from one form to another.
    Example: A pendulum converts potential energy to kinetic energy and back.
  2. Why does a charged balloon stick to a wall?
    Answer: The balloon becomes charged by rubbing, inducing opposite charges on the wall, causing attraction.
    Example: Static cling of clothes.
  3. Explain why an object thrown vertically upwards slows down.
    Answer: Gravity acts downward, opposing the motion and reducing velocity until it stops at the highest point.
    Example: A ball thrown up eventually falls down.
  4. What causes refraction of light?
    Answer: Change in speed of light when passing from one medium to another.
    Example: Straw appears bent in a glass of water.
  5. Define amplitude of a wave.
    Answer: Maximum displacement of particles from their rest position.
    Example: Loud sounds have large amplitudes.
  6. Why are transformers used in electrical power systems?
    Answer: To increase or decrease voltage efficiently.
    Example: Step-up transformers increase voltage for transmission.
  7. What is the function of the nucleus in an atom?
    Answer: Contains protons and neutrons, holds most of the atom’s mass.
    Example: Determines atomic number and identity.
  8. Explain the term 'buoyancy.'
    Answer: Upward force exerted by a fluid opposing an object's weight.
    Example: Ships float due to buoyancy.
  9. What is meant by half-life of a radioactive substance?
    Answer: Time taken for half the radioactive atoms to decay.
    Example: Carbon-14 dating uses its half-life of 5730 years.
  10. Why does sound travel faster in warm air than in cold air?
    Answer: Molecules move faster in warm air, transmitting vibrations quicker.
    Example: Sounds carry better on hot days.
  11. What is the function of an ammeter?
    Answer: Measures electric current in a circuit.
    Example: Checking battery current.
  12. Define potential energy.
    Answer: Energy stored due to position or configuration.
    Example: Water stored behind a dam has potential energy.
  13. Explain why a vacuum flask keeps liquids hot or cold.
    Answer: Vacuum prevents heat transfer by conduction and convection; reflective surfaces reduce radiation.
    Example: Thermos bottles.
  14. What happens to the frequency of a wave when its speed decreases but wavelength remains constant?
    Answer: Frequency decreases because speed = frequency Γ— wavelength.
    Example: Sound waves in cooler air have lower speed and frequency.
  15. Why does a metal rod expand when heated?
    Answer: Particles vibrate more and take up more space.
    Example: Railway tracks have expansion gaps.
  16. Explain why we see lightning before hearing thunder.
    Answer: Light travels faster than sound.
    Example: Thunderstorm observations.
  17. What is the role of a resistor in an electric circuit?
    Answer: Limits current flow and drops voltage.
    Example: Protects LED circuits.
  18. Define velocity.
    Answer: Speed in a given direction.
    Example: 50 km/h east.
  19. Why do sound waves require a medium to travel?
    Answer: They are mechanical waves caused by particle vibrations.
    Example: No sound in space.
  20. What is the effect of increasing the cross-sectional area of a wire on its resistance?
    Answer: Resistance decreases because electrons have more paths.
    Example: Thick cables carry more current.

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