This equation describes a linear thermal expansion, which we’ll examine in the context of a metal bar expanding and increasing its length:
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In this equation, delta L is the change in length of the bar, delta T is the change in temperature of the bar, L is the original length before the temperature changed, and alpha is the linear coefficient of thermal expansion. The coefficient is just a number that represents how much the material expands. Metals, for example, tend to expand more than plastics.