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- Question
The base of an electric iron is brightly polished mainly
Options- A. to make it smooth and frictionless
- B. to make it rust-proof
- C. to reduce heat loss by radiation
- D. to make it more durable
- Correct Answer
- to reduce heat loss by radiation
ExplanationPolished surfaces are poor radiators of heat. So loss of heat on that account is reduced and the electric iron remains hotter than otherwise.
- 1. Mirage is an example of
Options- A. Reflection of light & Refraction of light
- B. Dispersion of light
- C. Total Internal Reflection
- D. Refraction of light & Total Internal Reflection of light Discuss
- 2. Skating on ice is possible because
Options- A. the surface of ice is smooth
- B. ice is cold
- C. the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
- D. the pressure on the ice due to skate raises its melting point Discuss
- 3. In a freezer ice cubes will be formed more quickly in trays made of
Options- A. rubber
- B. plastic
- C. aluminium
- D. wood Discuss
- 4. When body is accelerated
Options- A. its velocity never changes
- B. its speed always changes
- C. its direction always changes
- D. its speed may or maynot change Discuss
- 5. Pieces of camphor placed on water move about rapidly. This is because of
Options- A. diffusion
- B. viscosity
- C. surface tension
- D. capillarity Discuss
- 6. A ball is thrown vertically upwards. Assuming the air resistance to be constant and cosiderable:
Options- A. the time of ascent < the time of descent
- B. the time of ascent > the time of descent
- C. the time of ascent = the time of descent
- D. none of these Discuss
- 7. Pick out the only scalar quantity
Options- A. power
- B. Electric field
- C. magnetic momentum
- D. average velocity Discuss
- 8. A boat loaded with rocks floats in the middle of a swimming pool. A man in the boat throws the rocks overboard. The level of water in the pool will
Options- A. increase
- B. decrease
- C. remains the same
- D. first decrease and then increase Discuss
- 9. Total internal reflection can take place when light travels from
Options- A. Air to glass
- B. Air to water
- C. Water to glass
- D. Diamond to glass Discuss
- 10. The working of the quartz crystal in the watch is based on the
Options- A. Piezo - electric Effect
- B. Edison Effect
- C. Photoelectric Effect
- D. Johnson Effect Discuss
Physics problems
Search Results
Correct Answer: Refraction of light & Total Internal Reflection of light
Correct Answer: the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
Explanation:
Here is a case of lowering of melting point of ice with increase of pressure
Correct Answer: aluminium
Explanation:
Aluminium being a good conductor of heat conducts away the heat from the substance quite easily and causes quick freezing.
Correct Answer: its speed may or maynot change
Correct Answer: surface tension
Explanation:
The Camphor slowly dissolves in the water lowering the latter's surface tension in the immediate neighbourhood. The stronger pull exerted by the uncontaminated portion of water brings about a movement of the surface and the camphor particles are carried along with it. When after sometime the whole surface settles for the reduced tension, the movement of the camphor too short.
Correct Answer: the time of ascent < the time of descent
Correct Answer: power
Correct Answer: decrease
Explanation:
Let M and m grams be the mass of boat + rock in it. By law of floatation(M+m) grams of water will be displaced. This has a volume of (M+m)cc. That means the level of water in pool has risen up by (M+m)cc with the boat + rock when it is floating. If the rocks in the boat are thrown not into the pool but outside, the weight left is only M grams the weight of the boat. This will have displaced M cc of water only i.e less water than in the case of loaded boat. But if the rocks are put in the water in the pool and not outside, then the water in the pool will rise not only by M cc on account of empty boat but also by a volume of the stone put into it. This volume will be where m is the mass of rock and d density of rock.
Now is < m. Thus the total rise will be which is < M + m.
Correct Answer: Diamond to glass
Correct Answer: Piezo - electric Effect
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