Science Quiz 1

Science Quiz 1:

Physics:

1. Why does the surface of smooth road appear wet under the hot sun?

Ans: Under the hot sun the different layers of air differ in temprature, so their density differs causing            a mirage effect.


2. Why is mercury used in thermometers?

Ans: It is a good conductor of heat, and expands uniformly on heating.


3. Why is the tea set mad of clay and not metal?

Ans: Metal are good conductors of heat, so metallic tea sets will get hot or cold soon. But clay is a             bad conductor of heat.


4. Why is a compass used as an indicator of direction?

Ans: The megnetic needle of a compass always lies in north-south direction under the influence of              earth's megnetic field.


5. Why does radio reception improve after sunset?

Ans: After sun set there are no ionising radiations from the sun and so ionosphere which reflects                 radio waves becomes more stable. This improves radio reception.

6. Why does a body immersed in water weigh less?

Ans: The body experience an upward thrust of water.


7. Which reading on both centigrade and farenheit thermometers will be the same?

Ans: -40 degree centigrade.


8. What keeps the glider up in the air?

Ans: Upward thrust of the air.


9. Why is the driving mirror usually convex and not plain?

Ans: Its focal length is long,so it gives a wider field of view.It gives virtual,erect and dimished                     images.


10. Why do the clothes keep us warm during winter?

Ans: Clothes prevent the heat of the body from escaping.

11. Water preserved in porous vessel is cooler, why?

Ans: Water coming out of the pores evaporates and takes heat from the water of the container.


12. Why does the sun appear red while setting?

Ans: Sun being near the horizon, the rays have to travel a long distance. The red colour has the                   longest wavelength;  other colours of which the sun rays are composed have shorter wavelength,         so the latter are scattered by the  dust particles while only the red colour is able to penetrate.


13.  How does the fish live in the river where water is frozen?

Ans: Water has a maximum density at 4 degree centigrade while ice is formed at 0 degree centigrade            temperature. Ice formation always starts from the top in river or lake, so fish can live.

14.  Why does the water at higher altitudes not boil below 105 degree centigrade?

Ans: At high altitudes atmospheric pressure is low and boiling point of every liquid is proportional to         the atmospheric pressure.