Today we are sharing some General awareness Questions and answers. It will be helpful for some competitive examinations.
1. How does a clinical thermometer differ from an ordinary thermometer?
Ans. Clinical thermometer has a constriction near its bulb so that the mercury level is having risen to a height inside the tube, may not fall without being given a jerk and its correct reading may be taken.
2. Why do we not see things double with two eyes?
Ans. We do not see double with it no eyes as both images of an object fall on exactly similar parts of the two retinas of the two eyes. The reflection is therefore simultaneous. Hence there is only one vision with two eyes.
3. Why does radio reception improve after sunset?
Ans. After sunset no ionising radiations are emitted from the sun so ionosphere which reflects radio waves becomes more stable. This improves radio reception.
4. Why do we hear a sound like the roaring of a sea when we hold a sea shell to our ear?
Ans. The curved surface of the sea shell causes reflections of the sound which in turn cause vibrations producing sound like the roar of a sea.
5. Why are lubricants used in machines?
Ans. In machines heat is produced due to friction by metal-to-metal contact. Lubrication minimises the heat caused by friction and hence reduces wear and tear of the surface in contact.
6. The moon is constantly falling towards the earth, but it can never hit the earth. Why?
Ans. According to Newton, moon has just the right speed to keep moving around the earth in a nearly circular orbit. Though it is constantly falling towards the earth it cannot hit the earth because the earth’s surface curves down under it by the same amount.
7. If a pendulum is taken to the mountain, what will be the effect on its time-period?
Ans. The time-period of the pendulum will increase i.e. it will go slow if it is taken to a mountain because the time period of a pendulum is inversely proportional to the square root of ‘g’, the acceleration due to gravity.
8. Why is electrical wiring in parallel better?
Ans. Electrical wiring in parallel is better because all the lines will have the same potential difference and if one line gets fused the other lines are unaffected.
9. What happens if a stone is thrown parallel to the surface of the earth from the roof of a building?
Ans. Due to the attraction of the earth, the direction of motion of the stone will change every instant and the stone will strike the ground some distance away from the building.
10. Why do thick bottomed drinking glasses frequently crack, if hot water is poured into them?
Ans. We know that glass is a bad conductor of heat, that is, it does not allow the heat to conduct quickly to the lower surface. The two surfaces of glass are at two different temperatures and expand differently. This irregular expansion causes the breakage of the glass at the bottom.
11. An aero plane flying at high altitude leaves a white trail behind. Why?
Ans. At lower altitude the density of air is more than that of the smoke given by the aero plane. The smoke is lifted upwards and mixes with air easily. But at higher altitudes the density of air is lower and a stage comes where it is nearly equal to the density of smoke and the smoke particles cannot readily go up and mix with air, instead they form a white stream of their own in the sky.
12. How can a man skate on ice?
Ans. In skating the whole weight of the body is supported on the edge of the skate and the resulting pressure causes a little ice to melt below the edges of the skate which enables it to avoid a slip.
13. Why does a swimming pool appear less deep than it really is?
Ans. When rays of light start from the bottom of a pool and travel from water to air then they are refracted away from the normal because they travel from denser medium to rarer medium. As a result a virtual image of the bottom is formed above the bottom. Hence, a swimming pool appears less deep.
14. When a person lies on a cushion, the depression is not so much as when he stands on it. Why?
Ans. It is a well known fact that the total weight is spread over a large area the pressure will be small. If the total weight acts on a small area, the pressure will be large.
15. Why is diesel oil preferred for heavy road vehicles?
Ans. As compared to other fuels used in internal combustion engines, diesel oil has higher efficiency of combustion and is much more economical. About 40% of the fat produced by it is used and the mechanism of diesel oil engines is simpler than that of the other engines.
16. Why, in the construction of bridges, are the ends of the steel girders not fixed but placed on rollers?
Ans. In the construction of a bridge, the ends of the steel girders are not fixed but are placed on rollers so that they can expand or contract freely.
17. Why do the dogs stick out their tongue during hot weather?
Ans. Dogs cannot perspire through the skin, so they stick out their tongue during hot weather in order to achieve a cooling effect.
18. How is the cooling effect in a domestic refrigerator achieved?
Ans. The cooling effect in a domestic refrigerator is achieved when a volatile liquid (Freon) evaporates inside the copper coils surrounding the freezer box. The necessary latent heat is provided by the liquid itself which, therefore, cools. The evaporated Freon is compressed so as to convert it into liquid Freon which can be recycled and evaporated again in acyclic process.
19. Why is a concave mirror used for shaving?
Ans. The concave mirror produces a magnified and correct image of the face. Since a large image of the face is seen in the concave mirror, it becomes easier to make a smooth shave.
20. Why are convex mirrors used in automobiles?
Ans. Convex mirrors are used as rear-view mirror in automobiles to see the traffic at the back side because it produces right upside and diminished image of the objects, so a wider field of view is obtained on the mirror.