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State one limitation of solar energy available from solar cells.
What is the minimum wind velocity required to obtain useful energy with a windmill?
Explain why is the solar cooker box covered with a plane glass plate?
List any four areas where solar cells are being used as a source of energy.
Write two advantages of classifying energy sources as renewable and non-renewable.
(a) Classify the two fuels – CNG and hydrogen – as renewable and non-renewable.
(b) Justify the statement, “Hydrogen is a cleaner and better fuel than CNG”.
What is the importance of hydropower plants in India? Describe how electric energy is generated in such plants.
A student constructed a box type solar cooker. He found that it is not working efficiently. What could this be due to? Give any four possible mistakes in the construction and operation of the solar cooker. What can maximum temperature ordinarily be reached inside a solar cooker?
Name the three forms in which energy from oceans is made available for use. What are OTEC power plants? How do they operate?
Draw a labelled diagram of floating gas holder type biogas plant and describe it's working. Mention any two advantage of using animal dung for making biogas over using it as a fuel in the form of dried dung cakes.
Which of the following is not a non- renewable source of energy?
The fraction of sun’s energy received on the earth is about:
Which of the following sources of energy is different from the other?
Choose the only renewable source of energy from the following:
The longest and the shortest wavelengths (in micron) for red and violet light are respectively:
The nuclear fuel in the sun is:
Minimum velocity of wind required for a functional windmill is about:
The temperature difference required up to a water level difference of 1000 m for operating an OTEC system is:
The energy liberated by wood on burning is:
Which of the following is not obtained by the destructive distillation of wood?
The energy liberated by charcoal on burning is:
Amount of charcoal produced on the destructive distillation of 1 kg of wood is about:
Which of the following is not a fossil fuel?
The average amount of energy released during the fission of uranium atom is:
Write true or false for the following statements:
Solar energy has the greatest potential of all the renewable sources of energies.
Reflectors are used in solar heating devices to concentrate the sun heat.
Black surfaces are poor absorbers of heat.
Glass cover in a solar heating device allows the short wavelength of ultraviolet radiations to enter the solar cooker.
Spherical reflectors are used to obtain high temperatures in solar heating devices.
Solar cells are made of semiconductor materials.
A modern selenium solar cell can convert 25% of sunlight into electrical energy.
Solar cells and solar panels cannot be used in remote areas.