What are the advantages of nuclear energy?
The nuclear energy advantages are as follows:
a) Fusion of four hydrogen atoms produces a huge amount of energy approximately equal to 27 MeV.
b) Large amount of energy is produced per unit mass.
c) It does not produce smoke. It is clean energy.
d) Fission of one atom of uranium produces 10 million times the energy released by burning of one atom of carbon.
Can any source of energy be pollution-free? Why or why not?
What are the limitations of the energy that can be obtained from the oceans?
If you could use any source of energy for heating your food, which one would you use and why?
What is a good source of energy?
On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?
Which of the following is not an example of a bio-mass energy source?
(a) wood (b) gobar-gas
(c) nuclear energy (d) coal
What are the disadvantages of fossil fuels?
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
What are the qualities of an ideal source of energy?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Choose the correct option.
A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each
(a) two revolutions (b) one revolution
(c) half revolution (d) one-fourth revolution
Find out, from Table 10.3, the medium having highest optical density. Also find the medium with lowest optical density.
Material medium |
Refractive index |
Material medium |
Refractive index |
Air | 1.0003 | Canada Balsam |
1.53 |
Ice | 1.31 | ||
Water | 1.33 | Rock salt | 1.54 |
Alcohol | 1.36 | ||
Kerosene | 1.44 | Carbon disulphide |
1.63 |
Fused quartz |
1.46 | ||
Turpentine oil |
1.47 | Ruby | 1.71 |
Benzene | 1.50 | Sapphire | 1.77 |
Crown glass |
1.52 | Diamond | 2.42 |
Table 10.3 Absolute refractive index of some material media
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?
(a) Between the principal focus and the centre of curvature
(b) At the centre of curvature
(c) Beyond the centre of curvature
(d) Between the pole of the mirror and its principal focus.
Metallic oxides of zinc, magnesium and copper were heated with the following metals.
Metal | Zinc | Magnesium | Copper |
---|---|---|---|
Zinc oxide | |||
Magnesium oxide | |||
Cooper oxide |
In which cases will you find displacement reactions taking place?
Calculate the number of electrons constituting one coulomb of charge.
Define 1 dioptre of power of a lens.
What is ozone and how does it affect any ecosystem?
What is the role of the brain in reflex action?
Find out the source of water in your region/locality. Is water from this source available to all people living in that area?
Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H2SO4.