Q1: Metallic surveying tapes are made of __________ which has a low co-efficient of expansion & enough strength.

ANS:A - invar

Metallic surveying tapes are made of Invar, which has a low coefficient of expansion and sufficient strength. Explanation:

1. Invar: Invar is an iron-nickel alloy known for its low coefficient of thermal expansion (CTE), which means it expands and contracts very little with changes in temperature. Invar typically contains about 36% nickel and 64% iron, although variations in composition exist.
2. Low Coefficient of Expansion: The low coefficient of expansion of Invar makes it ideal for applications where dimensional stability is critical, such as in surveying tapes. When subjected to temperature changes, Invar experiences minimal dimensional changes compared to other materials, ensuring accurate measurements over a wide range of temperatures.
3. Strength: In addition to its low coefficient of expansion, Invar also offers sufficient strength for the intended application. While not as strong as some other alloys like steel, Invar possesses adequate mechanical properties to withstand the stresses encountered during typical surveying operations.
4. Other Considerations:
   • Hastelloy: Hastelloy is a family of nickel-based alloys known for their excellent corrosion resistance in a wide range of environments. While some Hastelloy grades may offer good strength and thermal stability, they are not typically chosen for surveying tapes due to their higher cost and different properties compared to Invar.
   • Duralumin: Duralumin is an aluminum alloy that contains copper, manganese, and magnesium. While it offers good strength-to-weight ratio and corrosion resistance, it does not possess the low coefficient of expansion required for surveying tapes.
   • Monel Metal: Monel is a group of nickel-copper alloys known for their high corrosion resistance, particularly in marine environments. Like Hastelloy, Monel is not typically used for surveying tapes due to its different properties and higher cost compared to Invar.