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JAMB Physics 2013 Paper

Question : 13

Total: 43

Solution:

Concept:

Linear expansivity describes how a material's length changes with temperature.

Explanation:

The formula for linear expansion is

L = L_0(1 + \alpha \Delta\theta)

Initial length,

L_0 = 100.0\,\text{m}

\theta_0 = 30^\circ\text{C}

Final temperature is

-10^\circ\text{C}

, so the temperature change is:

\Delta\theta = -10 - 30 = -40\,\text{K}

Given

\alpha = 2 \times 10^{-5}\,\text{K}^{-1}

Substitute into the formula:

L = 100(1 + 2\times10^{-5}(-40))

L = 100(1 - 0.0008)

L = 100 \times 0.9992 = 99.92\,\text{m}

The wire contracts because the temperature decreased.

Answer:

99.92\,\text{m}

(Option D).

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