CBSE Class 10 Science Advanced Physics Source of Energy Nuclear Fission and Fusion Very Short Answer Questions Set 01

Very Short Answer Type

Question 1. State two source of energy which is non renewable in nature.
Answer:
Coal and petroleum (natural gas is also non-renewable). They formed over millions of years and cannot be replaced once used.
In simple words: Fossil fuels such as coal and petroleum will run out.

Teacher's Note:
1. Non-renewable sources are the conventional ones.
2. Name sources that exist in limited stock.

Question 2. State the type of energy in which a solar cell convert heat and light energy.
Answer:
A solar cell converts light (solar) energy into electrical energy.
In simple words: Sunlight goes in and electricity comes out.

Teacher's Note:
1. This is the photovoltaic effect.
2. The output is direct current.

Question 3. What is tidal energy?
Answer:
The energy possessed by the rising and falling water of the sea (high tide and low tide), caused by the pull of the moon on sea water, is called tidal energy.
In simple words: Tidal energy is the energy of the sea moving up and down with the tides.

Teacher's Note:
1. Tides occur twice a day.
2. A tidal barrage with a turbine converts it into electricity.

Question 4. What are the limitations of wind energy?
Answer:
1. Wind is not available at all times and places.
2. Windmills work only when the wind is fast enough.
3. Wind speed changes with time and season, and it cannot be predicted.
4. The energy can be used only at the site where the wind blows.
In simple words: Wind is unreliable and cannot be carried from place to place.

Teacher's Note:
1. Mention at least three points.
2. Unpredictability is the key limitation.

Question 5. Name two renewable sources of energy?
Answer:
Solar energy and wind energy (also hydro, tidal, geothermal and biomass).
In simple words: Sources that nature supplies again and again are renewable.

Teacher's Note:
1. Give examples that really are inexhaustible.
2. Do not name coal or petroleum.

Question 6. Name any two radiations emitted by the sun that are not visible to human eye?
Answer:
Ultraviolet rays and infrared rays.
In simple words: UV has a wavelength shorter than violet; IR is longer than red.

Teacher's Note:
1. Visible light lies between 400 nm and 700 nm.
2. Both lie outside this range.

Question 7. Give three example each of solid fuel and liquid fuel.
Answer:
Solid fuels: wood, charcoal, coal (also coke, paraffin).
Liquid fuels: petrol, kerosene, diesel (also methanol).
In simple words: Name three from each group.

Teacher's Note:
1. Solid and liquid fuels are classified by their state.
2. Most liquid fuels come from petroleum.

Question 8. Name the radiations we used to get relief from bodyaches.
Answer:
Infrared rays are used for relief from body aches, because they produce heat.
In simple words: Infrared lamps give soothing heat.

Teacher's Note:
1. Infrared rays have a heating effect.
2. Every hot object emits them.

Question 9. Name any two type of energy available from the oceans.
Answer:
Tidal energy and ocean thermal energy (also sea-wave energy).
In simple words: The sea gives tidal, wave and thermal energy.

Teacher's Note:
1. Name two forms, not two places.
2. OTEC uses temperature difference.

Question 10. Does the nuclear force depend on the charge of the particles?
Answer:
No. The nuclear force between two protons, two neutrons or a proton and a neutron is practically the same; it is independent of charge.
In simple words: Nuclear force does not care whether a particle is charged.

Teacher's Note:
1. This is why neutrons are held in the nucleus.
2. The nuclear force is attractive and short ranged.

Question 11. Uranium 235 has an atomic number 92, it has ___________ neutrons.
Answer:
Neutrons = A – Z = 235 – 92 = 143.
In simple words: Subtract the atomic number from the mass number.

Teacher's Note:
1. A = protons + neutrons.
2. Check: 92 + 143 = 235.

Question 12. Nuclear fission is the process of splitting of ____________ nucleus into ___________ nuclei.
Answer:
Nuclear fission is the splitting of a heavy nucleus into two lighter nuclei.
In simple words: A heavy nucleus breaks into two smaller ones.

Teacher's Note:
1. Uranium-235 is the standard example.
2. Neutrons and a lot of energy are released.

Question 13. Why is the fusion process called thermo-nuclear reaction?
Answer:
Fusion can take place only at extremely high temperatures (millions of kelvin) so that nuclei can overcome their electrostatic repulsion. Since it needs heat (thermo) and involves nuclei, it is called a thermonuclear reaction.
In simple words: It needs very high temperature to occur.

Teacher's Note:
1. Thermo means heat.
2. The Sun's energy is of this kind.

Question 14. Which process is responsible for energy generation in the sun?
Answer:
Nuclear fusion of hydrogen nuclei into helium.
In simple words: The Sun shines by fusing hydrogen.

Teacher's Note:
1. Hans Bethe proposed this in 1939.
2. Do not write fission.

Question 15. Is the energy released per nucleon in fission greater than that released during fusion?
Answer:
No. Per nucleon, fusion releases more energy than fission (for example, deuterium–tritium fusion gives about 3.5 MeV per nucleon, fission of uranium about 0.85 MeV per nucleon).
In simple words: Fusion gives more energy per nucleon.

Teacher's Note:
1. Compare energy divided by number of nucleons.
2. Fission gives more per reaction only because uranium has many nucleons.