Tricky Questions of EDS!!
1: In a vacum flask, silvering reduces the heat by what?
Ans: By radiation
2: The period of oscillation of a pendulum depends on?
Ans: Length of the pendulum.
3: The boiling point of a liquid______ if the pressure decreased.
Ans: Decreases
4: No sound is heard on the moon because there is a ____ on the moon.
Ans: No atmosphere
5: Why is Miners safty lamp save lamp?
Ans: The flame is covered by a guaze, so explosion does not occur on contact with inflammable gas.
6: Why do the photographic films get spoiled on exposure to light?
Ans: Silver bromide solution with which it is treated gets oxidized on exposure to light.
7: Why does Eno's salt give effervescence when water is added to it?
Ans: Becuase carbon dioxide comes out of the salt producing effervescence.
8: Why water pipes, in hilly areas, often burst on a cold frosty night?
Ans: Water in the pipes freezes and on freezing water expands, so pipes break.
9: Why do we sweat on a hot day?
Ans: In order to maintain a constant temperature the sweating is necessary on hot day.
10: What temperature in both the centigradeand fahrenheit thermometrs is the same?
Ans: -40
11: What is the name of mammal which lives in the sea?
Ans: Whale
12: Name the bird that does not fly.
Ans: Ostrich and Kiwi
13: Fanning produces coolness in the body.Why?
Ans: Because fanning produces fresh air to take the heat from the body.
14: What drops are put in the eyes to cause dilation of puplis?
Ans: Atropine.
15: Which phenomena concerning light explains the formation of the rainbow?
Ans: Refraction of light
16: Why do hair grow grey?
Ans: Due to the lack of certain nutrients for the hair.
17: How can bats fly in the dark?
Ans: The bats produce ultrasonic waves with their wings which are reflected back by the obstacles if any, and these reflected waves are detected by bats and they avoid obstacles.
18: Why does not moon have an atmosphere?
Ans: Moon's thinness is 10 times of the earth, so gases emencing from the surface escape into interplanetary vacum.
19: Why does the setting sun appear red?
Ans: Sun being near the horizon, the rays have to travel a long distance. The red colour has the longest wavelengths. So the other colours are scattered by the dust particles and only red penetrates.
20: Why do the two eyes give better vision than one?
Ans: With two eyes we get three-dimensional view of the object, so it's solidity and flatness are also seen.
21: Why is it dangerous to sleep in a closed roomwith a coal fire burning?
Ans: Burning coal gives Carbon monoxide and consumes oxygen of the room. Carbon monoxide is a poisonous gas and causes asphyxiation.
22: Why is a person in a moving vehicle thrown forward when the vehicle stops suddenly?
Ans: A person in a moving vehicle is in a state of motion. Though the vehicle suddenly stops his body remains in a state fo motion, so his body leans forward.
23: What preserved in a porous vessel is cooler.Why?
Ans: Water coming out of the pores evaporates and takes heat away form the water.
24: What is cause of night blindness?
Ans: Deficiency of vitamin A.
25: Why is driving mirror usually convex and not plane?
Ans: It's focal length is long, so it gives a wider fiels of view.
26: How do the fish live in the river where water is frozen?
Ans: Water has maximum density at 4C, and water under the surface is at this temperature. Water is frozen at the suface only so fish can live under the frozen surface.
27: Why is necessary to add manure or fertiliser to the field to get a good crop?
Ans: Plants take nutrients from the soil to grow and fertilisers supply these nutrients.
28: Why does milk turn soar?
Ans: Due to the action of bacteria.
29: Why does a plant cell have a large single vacuole than an animal cell?
Ans: A single plant cell contains 75% of water than an animal cell. So it is stored in single large vacoule.While animal cell has many small vacuoles.
30: Why is a small space left between each set of two rails of a railway line?
Ans: As the train moves, heat is produced due to friction and due to heat rail expand. If no space is left they will bend.
31: Why does a candle get extinguished when covered with tumbler?
Ans: Flame needs oxygen for burning nad covered flame will extinguish as soon as the supply of oxygen is finished.
32: Why does water put out fire?
Ans: Water does not allow the flame to come in contact with air to get oxygen.
33: How does oil fo the wick rise the flame?
Ans: Due to capillary action.
34: Why is kerosine oil poured on stagnant water to eradicate Malaria?
Ans: Kerosine oil, being lighter than water, floats over water and does not allow the pupae of the mosquito to breed.
35: A amn descending by parachute does it slowly.Why?
Ans: It's due to variation in pressure of the atmosphere.