TRANSITION Class 10th (Science)

What is the use of the black painted surface in solar heating devices? Black colour is a very good absorber of heat but a very poor reflector. So, it is used to absorb the maximum amount of heat from the sunlight. It is used in solar heating devices to maximise the absorption of heat and to minimise heat loss due to reflection. Give an example of indirect harnessing of solar energy. All green plants prepare carbohydrates from carbon dioxide and water in the presence of sunlight by the process of photosynthesis. All non-green plants and animals directly or indirectly consume food from the green plants (producers) and store this food in their bodies in the form of chemical energy. In other words, solar energy is transformed into chemical energy. State the important uses of wind energy. The wind energy is used: To generate electricity. To grind the wheat in flour mills. To run a pump to draw water from the ground. Write two advantages of classifying energy sources as renewable an...

Firewood is a conventional fuel. List any four reasons for replacing it with alternate sources of energy. Wood has low calorific value as compared to other sources of fuel. It causes air pollution on burning. Cutting down of trees causes depletion of forest leading to imbalance in nature. Only 8-10% energy of burning firewood is utilised and the remaining is wasted. State two advantages and two disadvantages of geothermal energy. Advantages: The use of geothermal energy does not cause any pollution. The use of geothermal energy is quite economical. Disadvantages: It is not available everywhere. Deep drilling in the Earth to obtain geothermal energy is very difficult. What is biogas? Why is biogas considered an ideal fuel for domestic use? Biogas is a combustible mixture of methane (about 75%), carbon dioxide, hydrogen and hydrogen sulphide gas. It is obtained by anaerobic decomposition of human and animal excreta and agricultural and urban waste materials. Biogas is consi...

1. Give the construction and working of a solar cooker. A device that utilises solar energy for cooking purposes is called a solar cooker. The most commonly used form of solar cooker is known as box-type solar cooker. A box-type solar cooker is shown in the figure. Construction of a box-type solar cooker:  A box-type solar cooker consists of the following components: Box (B):  This is an insulated metal or a wooden box. It is painted black from inside because black surface absorbs more heat. The box may be provided with four roll-wheels. There is a thermocol layer between the wooden box and the inner metal box. Glass cover (G):  A cover made of two sheets of toughened glass held together in an aluminium frame is used as a cover of the box B. Plane mirror reflector (R):  A plane mirror reflector fixed in a frame is fixed to the box B with the help of hinges. The mirror reflector can be positioned at any desired angle to the box. The mirror is positioned so ...

Which part of the solar cooker is responsible for greenhouse effect? The glass sheet in the solar cooker creates a greenhouse effect. Glass sheet has a property that allows the infra-red rays of shorter wavelength from the Sun to get in the device but does not allow the infra-red rays of longer wavelength to leave the solar heating device. Therefore, heat energy is trapped inside the heating device. Though wood is a renewable source of energy, but the use of wood as a fuel is not a wise decision. Explain. Wood is a renewable source of energy. It is obtained by cutting trees. A new plant sapling usually takes more than 15 years to grow and mature into a tree. Therefore, replenishment of cut down trees takes a very long time. Cutting down of trees causes depletion of the forests leading to imbalance in nature. Burning of wood also causes air pollution. Due to the above reasons, usage of wood as a source of energy is not a wise decision. Wavelength of radiation incident on a surface i...

Firewood is a conventional fuel. List any four reasons for replacing it with alternate sources of energy. Wood has low calorific value as compared to other sources of fuel. It causes air pollution on burning. Cutting down of trees causes depletion of forest leading to imbalance in nature. Only 8-10% energy of burning firewood is utilised and the remaining is wasted. State two advantages and two disadvantages of geothermal energy. Advantages: The use of geothermal energy does not cause any pollution. The use of geothermal energy is quite economical. Disadvantages: It is not available everywhere. Deep drilling in the Earth to obtain geothermal energy is very difficult. What is biogas? Why is biogas considered an ideal fuel for domestic use? Biogas is a combustible mixture of methane (about 75%), carbon dioxide, hydrogen and hydrogen sulphide gas. It is obtained by anaerobic decomposition of human and animal excreta and agricultural and urban waste materials. Biogas is consi...