# Physics General Knowledge Questions and Answers

Today we are sharing a pdf Study Material Covering Physics General Knowledge Questions and Answers. It includes 99 Questions and Answers. Some of the Questions and Answers are shown below.

1. Why a fuse used in the electrical circuits?
Answer: A fuse is used as a safety measure in the electrical circuit. A fuse is a wire of low melting point. When a heavy current passes through it, the metal gets heated up and melts, thus breaking the circuit.

2. Why do we hear better in water than on land?
Answer: This is because velocity of sound is greater in water than in air. Due to moisture, density of the medium decreases, hence velocity of sound increases.

3. Why a petrol fire cannot be extinguished by pouring water on it?
Answer: Water being heavier, slips down and petrol rises to the surface and continues to burn as before. Hence, water cannot be used for extinguishing petrol fire.

4. Why the flash of lightning seen before the sound of thunder is heard?
Answer: The velocity of light is much greater than that of the sound. Therefore flash of lightning is seen before the sound of thunder is heard.

5. Why is electric light filament made of tungsten?
Answer: Because tungsten has a high resistance. Hence, when electric current flows through the filament, enormous heat is produced due to its high resistance and the filament glows.

6. A rocket can go into space but a jet cannot why?
Answer: Jet engine is a gas turbine which produces a steam of hot gas enabling an aircraft to be propelled through the air by reaction of propulsion, while the rocket is a projectile driven by reaction of propulsion which contains its own propellants. A rocket unlike a jet is, therefore, independent of the earth’s atmosphere and is used in space.

7. Why it is difficult to walk on an icy surface?
Answer: We are able to walk due to the force of friction. On an icy surface the force of friction is negligible, hence it is difficult to walk on it.

8. Why does a man lean forward while climbing a hill?
Answer: A man leans forward so as to keep himself in stable equilibrium due to which he increases the base of the support so that the vertical line passing through the centre of gravity may fall with the base.

9. The sky appears blue, Why?
Answer: Violet and blue light have short wavelength and are scattered more than red light waves. While red light goes almost straight through the atmosphere, blue and violet are scattered by particles in the atmosphere. Thus we see a blue sky.

10. What causes the rumbling sound of thunder?
Answer: Air is heated instantly when an electrical charge of lightning passes through it. The heat causes the molecules of air to expand in all the directions. As the molecules seek more room, they collide violently with layers of cool air, and set up a great air wave that has the sound of thunder.

11. Why does a parachute must have a hole?
Answer: A hole in the centre of parachute is made to avoid oscillation of the parachute while descending owing to the changing currents of wind. The hole allows the air to run out of the parachute regularly.

12. How can bats fly in the dark avoiding obstacles?
Answer: The ultrasonic waves produced by bats during flying are reflected back when they hit the obstacles. Hence, bats can find their path without any difficulty.

13. Why is rainbow seen after rain?
Answer: After the rain some clouds continue to linger in the sky which contains water droplets. These water droplets act like prisms and sun’s rays falling on water droplets suffer dispersion and produce a spectrum. Hence, rainbow is seen.

14. How does the thermos flask keep the liquid hot for a long time?
Answer: Thermos flask is a double walled bottle with a vacuum between the walls. Because of this the loss or gain of heat through conduction, convection and radiation is reduced to a minimum.

15. Why steel is more elastic than rubber?
Answer: Steel is more elastic than rubber because strain produced in steel is less than that in rubber when same force is applied to both of them.