Explanation: A transformer is an electrical device used to increase (step-up) or decrease (step-down) the voltage of alternating current (A.C.). It works on the principle of electromagnetic induction and functions only with A.C., not with D.C. A transformer consists of two coils—primary and secondary—wound around a soft iron core. The voltage ratio between these coils depends on the number of turns in each winding. Transformers are used in power transmission, distribution, and electronic devices to regulate voltage levels efficiently.

Explanation: Mumps is a contagious viral disease caused by the mumps virus, a member of the Paramyxoviridae family (genus Rubulavirus). It primarily affects the salivary glands, especially the parotid glands, leading to painful swelling near the cheeks and jawline.

Mode of Transmission: The infection spreads through respiratory droplets or direct contact with saliva from an infected person.

Symptoms:

• Swelling and pain in the parotid glands (below the ears)
• Fever and headache
• Muscle pain and fatigue
• Difficulty in chewing or swallowing

Prevention: Mumps can be effectively prevented by the MMR vaccine (Measles, Mumps, and Rubella vaccine).

Explanation: The decibel (dB) is a unit used to measure the intensity or loudness of sound. It expresses sound level on a logarithmic scale relative to a standard reference intensity of 10^-12 watt/m², which is the faintest sound the average human ear can hear. Normal conversation is around 60 dB, city traffic about 80–90 dB, and sounds above 120 dB can cause pain or hearing damage. The decibel scale helps compare very large variations in sound intensity conveniently.

Explanation: The ATM (Automated Teller Machine) was invented by John Shepherd-Barron in 1967. He designed the first cash dispensing machine, which was installed by Barclays Bank in London, UK. The first ATM used special paper vouchers impregnated with a radioactive compound instead of plastic cards. The idea revolutionized the banking sector by allowing people to withdraw money anytime without visiting a bank counter. Modern ATMs now use magnetic or chip-based cards, PIN authentication, and networked systems for secure transactions.

Explanation: The burning of a candle is a chemical change because new substances such as carbon dioxide, water vapour, and heat energy are produced during the reaction between wax and oxygen. This change is irreversible and results in a permanent alteration of the chemical composition of the material. In contrast, melting of wax and vapourisation of water are physical changes since no new substances are formed and the process can be reversed by cooling.

Explanation: In computer programming, the term "Beans" is specifically associated with the Java programming language. A JavaBean is a reusable software component written in Java that can be manipulated visually in a builder tool. JavaBeans follow certain conventions such as having a no-argument constructor, providing getter and setter methods, and being serializable. They are widely used in Enterprise Java applications for data encapsulation and to promote modular, reusable code.

Explanation: In household electrical wiring, all the given statements are correct: the red insulated wire is the live (phase) wire, the black insulated wire is the neutral wire, and the green insulated wire is used for earthing to ensure safety by preventing electric shocks.

Sodium bicarbonate (NaHCO₃), also known as baking soda, is used in fire extinguishers. When heated, it decomposes to produce carbon dioxide (CO₂), which displaces oxygen and helps smother the fire. It is especially effective for extinguishing electrical and small grease fires.

• Sodium carbonate: Used in glass and soap making, not for fire control.
• Sodium nitrate: An oxidizing agent, not suitable for extinguishing fires.
• Sodium sulphate: Used in detergents and paper making, not in fire extinguishers.

Explanation: Producer gas is a mixture of flammable gases such as carbon monoxide (CO) and hydrogen (H₂), along with nonflammable gases like nitrogen (N₂) and carbon dioxide (CO₂). It is produced by the partial combustion of carbon-containing fuels (like coal or coke) with air and steam, and is used as a fuel in industrial furnaces.