CGPSC MAINS 2012 Paper-4

Points to Remember: Snell’s Law Refractive Index Relationship between angle of incidence and angle of refraction Reversal of light path Introduction: Refraction is the bending of light as it passes from one medium to another. This bending occurs because light travels at different speeds in different media. A classic example is observing a straw appearing … Read more

Points to Remember: Ohm’s Law describes the relationship between voltage, current, and resistance in an electrical circuit. It’s a fundamental principle in electrical engineering and physics. The law has limitations and doesn’t apply to all materials or situations. Introduction: Ohm’s Law is a fundamental principle in electricity, stating a direct proportionality between the voltage (V) … Read more

Points to Remember: Magnetic fields are invisible forces. Magnetic lines of force represent the direction and strength of a magnetic field. They are always closed loops. They never intersect. The density of lines indicates field strength. Introduction: Magnetism, a fundamental force of nature, is responsible for the attraction and repulsion of certain materials. While we … Read more

Points to Remember: Chlorophyll’s role in light absorption. Experiments demonstrating chlorophyll’s necessity. Comparison of chlorophyll-containing and chlorophyll-deficient plants. The chemical process of photosynthesis and chlorophyll’s involvement. Introduction: Photosynthesis, the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll, is fundamental to life on Earth. Chlorophyll, … Read more

Points to Remember: Definition of Lewis acid and Lewis base. Examples of Lewis acids and bases. Distinction between Lewis and Brønsted-Lowry definitions. Introduction: The concept of acids and bases is fundamental to chemistry. While the Brønsted-Lowry theory defines acids as proton donors and bases as proton acceptors, the Lewis theory provides a broader definition, encompassing … Read more

Points to Remember: The fundamental difference lies in the economic viability of extraction. Ores are minerals with commercial value, while minerals are naturally occurring inorganic substances. The concentration of a mineral determines whether it qualifies as an ore. Introduction: The terms “ore” and “mineral” are often used interchangeably, leading to confusion. However, a crucial distinction … Read more

Points to Remember: Sodium carbonate’s chemical formula and properties. Its behavior in aqueous solution (ionization, pH). The resulting ions and their interactions with water. Practical implications of its aqueous solution properties. Introduction: Sodium carbonate (Na₂CO₃), also known as washing soda or soda ash, is a common inorganic salt. It’s a white, crystalline powder that readily … Read more

Points to Remember: Bleaching powder’s chemical composition and properties. The oxidation process involved in bleaching. Different types of colored substances and their susceptibility to bleaching. Limitations and safety concerns associated with bleaching powder. Introduction: Bleaching powder, chemically known as calcium hypochlorite (Ca(ClO)₂), is a widely used bleaching agent. Its ability to decolorize substances stems from … Read more

Points to Remember: Basic working principle of a solar cell. Types of solar cells. Advantages and disadvantages of solar cells. Applications of solar cells. Future prospects of solar cell technology. Introduction: A solar cell, also known as a photovoltaic (PV) cell, is a semiconductor device that converts sunlight directly into electricity. This conversion is achieved … Read more