The transistor in an electronic device is used as a switch, for amplifying alternating signals, and in preventing overheating in electric irons.

Here are the solutions to the multiple-choice questions: 6. The transistor in an electronic device is used as a switch, for amplifying alternating signals, and in preventing overheating in electric irons. Transistors are primarily used as electronic switches and for amplifying electronic signals. Preventing overheating in electric irons is typically handled by a thermostat or fuse, not a transistor. The correct option is B. I and II only. 7. Which of the following statements about noble gases is correct? They are very reactive, diatomic molecules, monatomic molecules, charged gases. Noble gases are known for their low reactivity and exist as individual atoms, meaning they are monatomic molecules. The correct option is C. monatomic molecules. 8. The gas evolved when a small piece of sodium is dropped into a beaker containing water is When sodium reacts with water, it produces sodium hydroxide and hydrogen gas. The reaction is: 2Na(s) + 2H_2O(l) 2NaOH(aq) + H_2 (g) The correct option is C. hydrogen. 9. Hand trowel is used in farming to turn manure during compost making, transplant seedlings, remove weeds, level soil surface. A hand trowel is a small, scoop-shaped tool specifically designed for digging small holes and carefully moving plants, making it ideal for transplanting seedlings. The correct option is B. transplant seedlings. 10. The appropriate apparatus for the separation of a mixture of water and kerosene is Water and kerosene are immiscible liquids that separate into layers due to different densities. A separating funnel is used to separate such liquid mixtures. The correct option is D. separating funnel. 11. Two atoms of the same element with symbols ^12X and ^13X differ by their The superscript numbers (12 and 13) represent the mass number (number of protons + number of neutrons). Since they are atoms of the same element (X), they have the same number of protons (atomic number). Therefore, the difference in their mass numbers must be due to a difference in their neutron numbers. The correct option is B. neutron numbers. 12. In which of the following systems does the farmer rely on animals in case of crop failure? Mixed farming involves both crop cultivation and animal rearing. If crops fail, the farmer can still rely on the animals (for products like milk, meat, or for sale) as a source of income or food. The correct option is C. Mixed farming. 13. The bottom of a pool of water appears closer to the surface than it is. Which of the following properties accounts for this observation? This phenomenon occurs because light rays bend as they pass from water (a denser medium) into air (a less dense medium). This bending of light is called refraction. The correct option is B. Refraction. Drop the next question.