Photo AI
Select any two from (i), (ii) or (iii) below and explain the difference between the terms in each: (i) Optical pyrometer and thermocouple pyrometer; (ii) Grey cast iron and white cast iron; (iii) Upper critical temperature (UCT) and lower critical temperature (LCT). - Leaving Cert Engineering - Question c - 2021
Question c
Select any two from (i), (ii) or (iii) below and explain the difference between the terms in each: (i) Optical pyrometer and thermocouple pyrometer; (ii) Grey cast... show full transcript
Worked Solution & Example Answer:Select any two from (i), (ii) or (iii) below and explain the difference between the terms in each: (i) Optical pyrometer and thermocouple pyrometer; (ii) Grey cast iron and white cast iron; (iii) Upper critical temperature (UCT) and lower critical temperature (LCT). - Leaving Cert Engineering - Question c - 2021
Step 1
(i) Optical pyrometer and thermocouple pyrometer
Answer
To differentiate between the optical pyrometer and the thermocouple pyrometer:
Optical Pyrometer: An optical pyrometer measures the intensity of light from a hot object, typically a filament lamp. It operates by adjusting the light's color to match the color emitted by the object, allowing the user to determine its temperature based on the color correlation.
Thermocouple Pyrometer: A thermocouple pyrometer, on the other hand, operates on the principle of different thermal conductivity in two dissimilar metals. When joined, they create a junction that generates an electrical current proportional to the temperature difference, allowing for temperature measurement.
Step 2
(ii) Grey cast iron and white cast iron
Answer
The differences between grey cast iron and white cast iron include:
Grey Cast Iron: This type of iron has a grey color due to the presence of graphite flakes, which provide a ductile nature. It fractures easily and often has a good machinability due to its softer structure.
White Cast Iron: In contrast, white cast iron appears white when broken due to the absence of graphite. It is harder and more brittle compared to grey cast iron, making it less machinable, yet it offers significant wear resistance.
Step 3
(iii) Upper critical temperature (UCT) and lower critical temperature (LCT)
Answer
To explain the upper critical temperature (UCT) and lower critical temperature (LCT):
Upper Critical Temperature (UCT): This is the temperature at which a phase change occurs in metals, specifically during solidification. It signifies the upper limit of temperature for maintaining a given phase.
Lower Critical Temperature (LCT): Conversely, the lower critical temperature represents the temperature below which a material transitions from austenite to a pearlite structure, thus affecting its mechanical properties and transformation characteristics.