Physics quiz question: dimensional expansion of aluminum rod

Physics 205A Quiz 7, fall semester 2018
Cuesta College, San Luis Obispo, CA

An aluminum bar (linear expansion coefficient 2.3×10^–5 K^–1) has a length of 0.500 m, and a cross-sectional area of 4.0×10^–4 m² at room temperature (20.0° C). As the temperature of the bar is raised, its __________ will increase.
(A) length.
(B) cross-sectional area.
(C) (Both of the above choices.)
(D) (Neither of the above choices.)

Correct answer: (C)

The relation between the change in length (along any dimension) ∆L due to a temperature change ∆T is given by:

α·∆T = ∆L/L.

With a temperature increase, the length, width, and height of the bar will all proportionally expand, such that both the length and the cross-sectional area of the bar will increase.

Sections 70854, 70855
Exam code: quiz07PeA7
(A) : 25 students
(B) : 3 students
(C) : 22 students
(D) : 0 students

Success level: 44%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.13