The question asks why stainless steel resists rusting compared to ordinary iron. This involves understanding the composition of stainless steel and the chemical process of rusting.
B) The chromium content forms a protective oxide layer that isolates the iron from oxygen and moisture. This accurately describes the mechanism by which stainless steel resists rusting. The chromium forms a passive, stable oxide layer that prevents the iron from reacting with its environment.
The question asks about the composition of '18/8 stainless steel', a common alloy used in household items like cutlery and cookware. Understanding the nomenclature of stainless steel grades is key to answering this question.
B) 18% chromium and 8% nickel
This option correctly identifies the primary alloying elements and their approximate percentages in '18/8 stainless steel'. Chromium provides corrosion resistance, and nickel enhances ductility and strength, making it suitable for cutlery and cookware.
The question asks to distinguish between brass and bronze based on their typical compositions. This requires knowledge of common alloys and their primary constituent metals.
Correct Option: D) Brass is copper and zinc; bronze is copper and tin.
This statement accurately describes the primary compositions of both brass and bronze. Brass, known for its workability and acoustic properties, is an alloy of copper and zinc. Bronze, historically significant for tools and weapons, is an alloy of copper and tin, often with other additives.
The question asks about the primary characteristic for which Bell metal, a specific bronze variant with a higher proportion of tin, is valued. We need to identify the most significant property that makes it suitable for its common applications.
A) Sonorous (ringing) quality when struck — Bell metal's high tin content gives it a unique crystal structure that allows it to vibrate efficiently and produce a clear, sustained, and resonant sound when struck. This property is why it is historically and currently used for making bells, gongs, and other percussion instruments.
This question tests knowledge about the classification of alloys, specifically stainless steel. The key to classifying an alloy as 'ferrous' lies in identifying its primary base metal.
Correct Option: A) Iron
Stainless steel is an alloy where iron is the primary base metal, typically constituting the largest percentage by weight. This makes it a ferrous alloy.
The question asks to identify a use case that is NOT typical for brass, considering its mechanical limitations. This requires knowledge of brass properties and common applications of different materials in engineering and manufacturing.
Correct Option: A) Construction of heavy load-bearing bridge girders