General Science Questions (MCQs) for Competitive Examinations

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Magnetite (Fe3O4) typically contains about 70% iron by weight. It is black in color and strongly magnetic. Hematite (Fe2O3) contains about 60–70% iron. Limonite contains 35–50% iron. Siderite (FeCO3) contains about 48% iron. Magnetite is widely mined due to its high iron concentration compared to other ores.

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The Moon has been bombarded with large quantities of Helium-3 by the solar wind. It is thought that this isotope could provide safer nuclear energy in a fusion reactor, since it is not radioactive and would not produce dangerous waste products.

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Fermentation is an anaerobic chemical process that breaks down glucose molecules. In baking, yeast consumes sugar and converts it into carbon dioxide and alcohol, making the dough rise. This gas gets trapped in the strands of gluten, resulting in air pockets that cause the dough to rise and form the characteristic spongy texture of bread and cakes. Further, the creation of lactic and acetic acids during fermentation augments this dough handling process, improves flavor, enhances the texture, and extends the shelf-life of the baked products.

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Keratin is a family of fibrous structural proteins involved in making up the outer layer of human skin. It is also the key structural component of hair and nails. Cells in the epidermis contain a structural matrix of keratin, which makes this outermost layer of the skin almost waterproof, and along with collagen and elastin, gives skin its strength. It also makes up fish scales and crustacean shells, bird feathers and beaks, animal horns and hooves.

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Rings of cartilage are present in the throat, specifically in the trachea or windpipe, to ensure that the air passage does not collapse. These semi-circular rings provide the necessary structural support to keep the airway open regardless of pressure changes that occur during breathing. This is very important for maintaining a clear, open path for air to flow into our lungs for respiration.

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Jhum is a traditional form of shifting cultivation that is common in the North-East of India. Also known as slash and burn agriculture, it is practiced by the tribal groups in Arunachal Pradesh, Meghalaya, Mizoram and Nagaland and the hilly areas of Assam. Jhum involves clearing a piece of land by setting fire or clear felling and using the area for growing crops.

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Most cases of filariasis are caused by the parasite known as Wuchereria bancrofti. A wide range of mosquitoes can transmit this parasite, depending on the geographic area. In Africa, the most common vector is Anopheles while in the Americas, it is Culex quinquefasciatus. Aedes and Mansonia transmits transmit the infection in the Pacific and in Asia. Thus, Culex, Aedes and Anopheles mosquitoes serve as vector for W. bancrofti in transmission of the disease. Aedes mosquito causes dengue fever. Anopheles mosquito causes malaria. Culex mosquito causes filaria. A wide range of mosquitoes can transmit the parasite, depending on the geographic area. In Africa, the most common vector is Anopheles and in the Americas, it is Culex quinquefasciatus. [This question was wrongly framed in exam as “filaria is caused by__:”. GKtoday has edited it to make it correct.]

Notes:
Intensive farming is an agricultural intensification and mechanization system that aims to maximize yields from available land through various means, such as heavy use of pesticides and chemical fertilizers. It is characterized by a low fallow ratio, higher use of inputs such as capital and labour, and higher crop yields per unit land area.

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Newton’s Law of Cooling states that the rate of temperature of the body is proportional to the difference between the temperature of the body and that of the surrounding medium. When a body cools by radiation, then rate of cooling depends on: Nature of the radiating surface, that is, emissivity; Area of the radiating surface; Mass of the radiating surface; Specific heat of the radiating body; Temperature of radiating body and Temperature of the surrounding.

Notes:
The major proteins in milk are casein and whey. These two milk proteins are both excellent sources of all the essential amino acids, but they differ in one important aspect—whey is a fast-digesting protein and casein is a slow-digesting protein. As a food source, casein supplies amino acids, carbohydrates, and the two inorganic elements calcium and phosphorus.