2B sample questions, explained
6 questions from our free public 2B sample, with the answer, a worked explanation, and why each other option is not the answer. They are original exam-style questions written to the public syllabus, not questions from a real exam. Print 10 free 2B questions.
1. Low carbon steel is the lowest-priced steel and is used extensively for steam, water, fuel oil and compressed air piping. Above what approximate temperature is low carbon steel NOT recommended because graphitization may occur within the pipe material?
- A. 230°C
- B. 525°C
- C. 400°C
- D. 540°C
Show the answer and explanation
Answer: C. Low carbon steel is generally limited to service below about 400 to 425°C, depending on the reference (some codes flag prolonged service above about 425°C, or 800°F). Above that range it is not recommended because graphitization (the breaking down of steel into iron and carbon graphite, with failure occurring along lines of graphite concentration) may occur, so 400°C is the best answer here. 230°C is the steam temperature limit for grey cast iron, not the graphitization limit for low carbon steel. 525°C is the upper limit for certain low-chrome alloy steels, and 540°C is a typical central-station alloy steel steam piping temperature, both well above the carbon-steel limit.
Why the other options are not the answer
- A. 230 °C is the steam temperature limit for grey cast iron, not the graphitization limit for low carbon steel.
- B. 525 °C is the upper limit for certain low-chrome alloy steels, well above the carbon-steel limit.
- D. 540 °C is a typical central-station alloy steel steam piping temperature, well above the carbon-steel limit.
Question ID 2B1-C10-Q001 · Unit §12: Piping · Report an error
2. A refinery produces fuel oil by a process that uses heat and pressure to decompose heavier crude oil fractions, actually changing the hydrocarbon structure to yield more of the valuable lighter hydrocarbons such as gasoline. Which process is described?
- A. Centrifuging
- B. Cracking
- C. Distillation
- D. Sweetening
Show the answer and explanation
Answer: B. The process that uses heat and pressure to decompose heavier crude fractions and actually change the hydrocarbon structure to produce more lighter hydrocarbons (gasoline) is cracking. Distillation only separates oil into its constituent parts by vaporizing the lighter fractions without changing the hydrocarbon structure. Centrifuging is used to detect water and sediment in a sample, not to refine oil. Sweetening is the removal of hydrogen sulphide from sour natural gas, not an oil-refining decomposition process.
Why the other options are not the answer
- A. Centrifuging is used to check a sample for water and sediment, not to refine oil.
- C. Distillation separates crude into fractions by boiling point without changing the hydrocarbon structure.
- D. Sweetening removes hydrogen sulphide from sour natural gas; it is not an oil-cracking process.
Question ID 2B2-C01-Q001 · Unit §14: Power Plant Systems · Report an error
3. Boiler feedwater can be used to supply steam desuperheaters only under what condition?
- A. Only if the boiler feedwater conductivity exceeds 20 000 mmhos
- B. Only if the boiler feedwater contains added polymers
- C. Only if the boiler feedwater has been cycled up 50 to 100 times
- D. Only if the boiler feedwater is phosphate free
Show the answer and explanation
Answer: D. Boiler feedwater is a mixture of steam condensate and demineralized makeup containing amines and oxygen scavengers; it can be used to supply steam desuperheaters only if the water is phosphate free, since phosphate would carry into and deposit from the steam. Cycling up 50 to 100 times describes boiler blowdown, very high conductivity describes regen waste, and added polymers would disqualify rather than qualify the water for desuperheating.
Why the other options are not the answer
- A. Very high conductivity describes regeneration waste, not spray water.
- B. Added polymers would disqualify the water for desuperheating rather than qualify it.
- C. Cycling up 50 to 100 times describes boiler water and blowdown, not water fit for desuperheater spray.
Question ID 2B2-C02-Q023 · Unit §14: Power Plant Systems · Report an error
4. In the differentiation of fine particulate emissions, what does the designation 'PM10' specifically refer to?
- A. Particulate matter less than 2.5 microns in diameter that penetrates deep into the lungs
- B. Particulate matter that settles out within 10 metres of the stack base
- C. Particulate matter less than 10 microns in diameter, readily inhaled into the lungs
- D. Particulate concentration of 10 mg/m3 in the stack gases
Show the answer and explanation
Answer: C. PM10 is defined as particulate that is less than 10 microns in diameter and is readily inhaled into the lungs, where a micron equals 10^-6 m. The 2.5-micron description belongs to PM2.5, which penetrates deeper into the lungs. The designation is a particle-size standard, not a concentration value (mg/m3) or a settling-distance specification.
Why the other options are not the answer
- A. Particles under 2.5 microns are PM2.5, which penetrate deeper into the lungs.
- B. PM10 is a particle-size class, not a settling distance.
- D. PM10 is a particle-size class, not a concentration in mg/m3.
Question ID 2B2-C08-Q001 · Unit §17: Environmental Protection · Report an error
5. A vector of length 1.0 is rotated counterclockwise to generate a sine wave. When the vector has rotated to an angle of 30 degrees, what is the magnitude of its vertical component (the instantaneous value plotted on the sine wave)?
- A. 1.000
- B. 0.707
- C. 0.500
- D. 0.866
Show the answer and explanation
Answer: C. The instantaneous value equals the vector length multiplied by the sine of the rotation angle. With a length of 1.0 at 30 degrees, sin 30 = 0.5, so the vertical component is 0.5 x 1.0 = 0.5. The value 0.866 corresponds to 60 degrees (sin 60), 0.707 corresponds to 45 degrees, and 1.000 corresponds to 90 degrees where the full vector projects onto the vertical axis.
Why the other options are not the answer
- A. 1.000 is the vertical component at 90°, where the whole vector is vertical.
- B. 0.707 is sin 45°.
- D. 0.866 is sin 60°, not sin 30°.
Question ID 2B3-C01-Q001 · Unit §18: Electrotechnology · Report an error
6. Per the NEMA MG1 guideline cited for maximum-starts-over-time protection, how many starts are permitted with the motor initially at ambient temperature?
- A. Two starts in succession, coasting to reset between starts
- B. One start in succession, coasting to reset
- C. Three starts in a row, coasting to reset between starts
- D. Unlimited starts as long as cooling air is supplied
Show the answer and explanation
Answer: A. The NEMA MG1 standard allows two starts in succession, coasting to reset between starts, with the motor initially at ambient temperature, and one start when the motor is already at its rated-load operating temperature. A single start applies only to the hot-motor case, three starts exceeds the guideline, and unlimited starts ignores the heat-buildup risk that the protection guards against.
Why the other options are not the answer
- B. One start applies when the motor is already at its rated-load operating temperature, not at ambient.
- C. Three starts in a row exceeds the guideline.
- D. Unlimited starts ignores the heat build-up the protection guards against.
Question ID 2B3-C06-Q024 · Unit §18: Electrotechnology · Report an error
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