Alloys — Set 4
Chemistry · मिश्र धातुएं · Questions 31–40 of 50
Which of the following is a characteristic of alloys compared to pure metals?
Correct Answer: B. Lower melting point
Most alloys have a lower melting point than the pure metals from which they are made. This property is specifically exploited in alloys like solder and fuse wires. Mixing different atom sizes disrupts the regular metallic lattice, making the material harder but less ductile.
What are the constituent metals of 'Gun Metal'?
Correct Answer: B. Copper, Tin, and Zinc
Gun metal is a type of bronze that contains about 88% copper, 10% tin, and 2% zinc. It was originally used for making cannons because of its strength and resistance to corrosion. Today, it is used for making pump parts, valves, and gears.
Which alloy is used in the manufacture of precision balance beams and measuring tapes?
Correct Answer: B. Invar
Invar's minimal thermal expansion ensures that measuring tapes do not change length in different weather conditions. This reliability is essential for land surveying and high-precision scientific measurements. It contains 36% nickel, which provides this unique physical stability.
Duralumin is an alloy made of Aluminum, Copper, Magnesium, and which other element?
Correct Answer: A. Manganese
Duralumin consists of about 94% aluminum, 4% copper, and small amounts of magnesium and manganese. It is one of the earliest aluminum alloys to be hardened by heat treatment. Its high strength-to-weight ratio revolutionized the construction of zeppelins and early airplanes.
What is the main metal in 'Type Metal' used in printing presses?
Correct Answer: A. Lead
Type metal is an alloy of lead, tin, and antimony used for casting the characters in traditional printing. Antimony is added because it expands upon cooling, ensuring that the metal fills the mold completely for sharp letters. Lead provides the bulk and easy-melting characteristics needed for quick casting.
Which alloy is commonly referred to as 'White Gold' in the jewelry industry?
Correct Answer: A. Gold and Silver/Palladium
White gold is an alloy of gold and at least one white metal, like silver, palladium, or nickel. It is often plated with rhodium to give it a bright, reflective white finish. Pure gold is too soft for most jewelry, so it is always alloyed for durability.
Which alloy is primarily used to make the base of electric bulbs and household fixtures?
Correct Answer: D. Brass
Brass is used for bulb bases because it is a good conductor of electricity and is easy to shape. It also resists corrosion well, ensuring a long-lasting connection in electrical sockets. Most brass used today is recycled from older scrap metal.
What is 'Pewter' primarily composed of?
Correct Answer: B. Tin
Pewter is a malleable metal alloy consisting mostly of tin (85% to 99%), with the remainder being copper and antimony. Historically, it was used for household plates and cups before glass became common. Modern pewter is lead-free to ensure it is safe for food and drink.
Which alloy is used for making powerful magnets in modern headphones?
Correct Answer: B. Neodymium-Iron-Boron
Neodymium magnets are the strongest type of permanent magnet commercially available today. They allow for smaller and lighter speakers in headphones while maintaining high sound quality. These are part of the 'rare-earth' magnet family.
Babbitt metal is an alloy used primarily for what industrial part?
Correct Answer: A. Bearings
Babbitt metal is a tin-based or lead-based alloy designed to reduce friction in bearings. It is soft enough to allow any grit in the lubricant to embed in the metal rather than scratch the axle. This alloy was patented by Isaac Babbitt in 1839.