TIG welding employs thoriated tungsten electrodes primarily because such material____________________?
Show answer Hide answer
Answer: B. Has better electron emissivity
Explanation
Thorium additions improve thermionic electron emission in tungsten welding electrodes. Better electron emissivity facilitates easier arc starting and superior arc stability. The work function of the electrode surface is lowered by the thorium content. TIG welding uses non-consumable tungsten electrodes to maintain an electric arc. Pure tungsten has a high melting point but poor electron emission characteristics. Thoriated electrodes emit electrons smoothly at lower operating temperatures.
Welding fabricators use thoriated electrodes for precision TIG welding of various metals. Stable electric arcs ensure consistent weld bead penetration and high joint quality. Operators handle thoriated electrodes with care due to low-level radioactive thorium content. Current carrying capacity is a minor factor compared to electron emission improvements. Mechanical strength of tungsten is not the primary reason for adding thorium. Ease of electrode preparation does not dictate the fundamental physics of arc emission.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. The Bayer process involves the digestion of bauxite under pressure using___________________?
Show answer Hide answer
Answer: B. NaOH
The Bayer process digests crushed bauxite ore using hot sodium hydroxide solution. Sodium hydroxide dissolves aluminum-bearing minerals under elevated pressure and temperature. This chemical digestion separates insoluble...
Q2. Elevating the sulfur concentration in pig iron tends to render it________________?
Show answer Hide answer
Answer: B. Hard
Sulfur acts as a strong carbide stabilizer and undesirable impurity in pig iron. High sulfur concentrations promote extreme material hardness and brittle mechanical behavior. This impurity significantly impairs the overa...
Q3. Induced draft fans installed in large power plant boilers feature blades that are__________________?
Show answer Hide answer
Answer: B. Backward curved
Induced draft fans in power plants commonly use backward-curved blade designs. Backward-curved blades offer high operating efficiency and stable pressure characteristics. These fans handle hot, particulate-laden flue gas...
Q4. In a ________________ process, entropy rises without any degradation of energy ?
Show answer Hide answer
Answer: A. Isothermal expansion
Entropy rises during isothermal expansion because heat is added at constant temperature. No thermal energy is degraded into unavailable work because the process is reversible. The heat transferred divided by temperature...
Q5. Scuba diving equipment utilizes a mixture of helium and oxygen because helium is____________________?
Show answer Hide answer
Answer: B. Not soluble in blood at high pressure
Helium has extremely low solubility in human blood and tissues under high pressure. This low solubility prevents nitrogen narcosis and painful decompression sickness bends. Divers breathe helium oxygen mixes safely durin...
Q6. The iron content in Indian iron ores is approximately _________________ percent?
Show answer Hide answer
Answer: B. 60-65
High-grade iron ores found in India contain approximately 60 to 65 percent iron. Hematite is the primary mineral form found in these rich domestic deposits. This high iron concentration makes the ore economically viable...