Which statement about CTE values among copper, brass, and aluminum is correct?

Which statement about CTE values among copper, brass, and aluminum is correct?

• A. Copper has the highest CTE.
• B. Brass has the lowest CTE.
• C. Aluminum has the highest CTE.
• D. Copper is about 17-18 ppm/C; Brass about 19 ppm/C; Aluminum about 24 ppm/C.

Answer: (D)

CTE is how much a material’s length changes with a change in temperature, usually expressed in ppm per degree Celsius. For copper, brass, and aluminum, aluminum expands the most per degree, copper the least, and brass falls in between. Typical values are about copper 17–18 ppm/°C, brass around 19 ppm/°C, and aluminum about 24 ppm/°C. This makes the statement that lists these approximate values the best fit, because it reflects both the magnitudes and the correct order. The other statements contradict these general data: copper is not the highest, aluminum is not the lowest, and brass is not the lowest either.

CTE is how much a material’s length changes with a change in temperature, usually expressed in ppm per degree Celsius. For copper, brass, and aluminum, aluminum expands the most per degree, copper the least, and brass falls in between. Typical values are about copper 17–18 ppm/°C, brass around 19 ppm/°C, and aluminum about 24 ppm/°C. This makes the statement that lists these approximate values the best fit, because it reflects both the magnitudes and the correct order. The other statements contradict these general data: copper is not the highest, aluminum is not the lowest, and brass is not the lowest either.