wht r the most important questions for tommkrpw 's physics paper ?
Answers
Hey,
Which grade?Cbse?Dubai?
If grade 9 then...here u goooooooo
Q. Mention two uses of isotopes in the field of medicine.
Ans.
(i) An isotope of cobalt is used in the treatment of cancer.
(ii) An isotope of iodine is used in the treatment of goitre.
Q. Who discovered vaccine for the first time?
Ans.
Edward Jenner discovered vaccine for the first time.
Q. (a) Name two properties of a substance to check its purity?
(b) Alloys cannot be separated by physical means, though it is considered mixture, Why?
Ans.
(a) A pure substance has a fixed melting point or boiling point at constant pressure. The purity of a substance can be tested by checking its melting point or boiling point. If a substance is impure i.e. it contains traces of another substance, the melting and boiling point of that substance will change.
(b) Alloys are homogeneous mixtures of metals and cannot be separated into their components by physical methods. But still, an alloy is considered as a mixture because it shows the properties of its constituents and can have variable composition.
Q. Is it possible that an object is in the state of accelerated motion due to external force acting on it, but no work is being done by the force? Explain it with an example.
Ans.
Yes, it is possible, if an object is moving in a circular path because in that case the centripetal force always acts perpendicular to the direction of displacement.
For example: Consider the motion of earth around sun. The earth is constantly moving in a direction perpendicular to the gravitation pull of sun, hence work done by the gravitational force is zero.
Get here the complete set of CBSE Class 9 Science: Important Short Answer Type Questions
Hope it helps!!!!
:)
CURRENT ELECTRICITY.....
Q. 1. Define 'current' .
Q. 2. State and define the SI unit of current.
Q. 3. Define the term 'electric potential'.
Q. 4. What do you mean by potential difference between two points ?
Q. 5. State and define the SI unit of potential difference.
Q. 6. What do you mean by conventional current ?
Q. 7. What do you mean by high potential and low potential ?
Q. 8. What do you mean by electrical resistance ? State and explain the factors on which it depends.
Q. 9. State and define the SI unit of resistance.
Q. 10. State Ohm's law. What are its limitations ?
Q. 11. What is the mathematical form of Ohm's law ?
Q. 12. Differentiate between ohmic and non-ohmic conductors. State few examples of each.
Q. 13. What do you mean by specific resistance (resistivity) of a material ? What is its SI unit ?
Q. 14. State two examples of each of the following:
material whose resistance increases with increase in temperature.
material whose resistance decreases with increase in temperature.
material whose resistance is not affected by change in temperature.
Q. 15. Name the materials used for making connection wire.Give reason for your answer.
Q. 16. Why and which materials are used for making standard resistors ?
Q. 17. What is an electric cell ? What type of energy conversion takes place in it while in use ?
Q. 18. Define the terms e.m.f. and terminal voltage of an electric cell ? State their unit.
Q. 19. Differentiate between e.m.f. and terminal voltage of a cell.
Q. 20. Difine internal resistance of a cell. What is its unit ?
Q. 21. State and explain the factors on which internal resistance of a cell depends.
Q. 22. Write a relation between e.m.f., terminal voltage and internal resistance of a cell.
Q. 23. Differentiate between series and parallel combination of resistances.
Q. 24. What do you mean by power-voltage rating of an appliance ?
Q. 25. Write a relation between watt ,volt and ampere.
Q. 26. What is the commercial unit of electrical energy ? Express it in its SI < value.
Q. 27. Differentiate between kilowatt and kilowatt-hour..........
CALORIEMETRY
Q. 1. Does the boiling point of water changes with altitude ? If so, how ?
Q. 2. Define specific latent heat of vaporisation.
Q. 3. Which material is the calorimeter commonly made of ?
Q. 4. 1 kg of ice at 0ºC is being continuously heated through an electric heater of 1kW. Assuming that all the heat is transmitted to ice, calculate the time interval in second for :
ice to completely melt to water at 0ºC,
water to get heated from 0ºC to 100ºC,
water at 100ºC to convert into steam.
[Given : Specific latent heat of ice= 3,36,000 J kg-1K-1
Specific heat capacity of water = 4,2200 J kg-1 K-1
Specific latent heat of steam = 22,60,000 J kg-1 K-1]
Ans. (i) 336 s (ii) 420 s (iii) 2,260 s
Q. 5. A given liquid changes into the gaseous state at a fixed temperature as well as at all temperatures.
(i) Name the process that takes place in each of the above two cases.
(ii) Mention two points of difference between the two cases in (i) above.
Q. 6. Define the term specific heat capacity of a substance. Give its SI unit.
A 30 g ice cube at 0ºC is dropped into 200 g of water at 30ºC. Calculate the final
temperature of water when all the ice cube has melted.
Given : Latent heat of ice = 80 cal g-1; Specific heat capacity of water = 1 cal g-1ºC-1
Ans. 15.65ºC
Q. 7. Explain how the following factors affect the rate of evaporation of a liquid :
Temperature of the liquid
Area of the exposed surface
Moisture in the surrounding air.
Q. 8. Define specific latent heat of fusion of ice. Give its SI unit.
Q. 9. What is the effect of increase in pressure on the melting point of ice and boiling point of water ?
Q.10. A piece of metal at 10ºC has a mass of 50 g. When it is immersed in a current of steam at 100ºC, 0.7 g of steam is condensed on it. Calculate the specific heat of metal.