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We would like to make a vessel whose volume does not change with temperature. We can use brass and iron \left (\beta _{brass} = \frac{6 \times 10^{-6}}{K} and \beta _{iron} = \frac{3.55 \times 10^{-5}}{K} \right )to create a volume of 100 cc. How do you think you can achieve this?

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For, the above situation, we need to make a double container whose volume difference will be 100cc.

Let us consider V_{1i}& V_{1b} as the initial volumes of the iron and brass container, i.e., V_{1i}- V_{1b} =100cc.

After heating by \Delta TK the difference will be the same, but the new volumes will be V2i &V2b.

Now, V_{2i}- V_{2b} =100cc

\gamma = \frac{\Delta V}{V\Delta T}

Therefore, V_{2} - V_{1} = \gamma V_{1}\Delta T

V_{2} =V_{1}+ \gamma V_{1}\Delta T

            = V_{1} (1 + \gamma \Delta T)

V_{2i}= V_{1i} (1 + \gamma_{i} \Delta T)

  & V_{2b} = V_{1b} (1 + \gamma _{b}\Delta T)

 V_{1i} + V_{1i}\gamma _{i}\Delta T - (V_{ib} + V_{ib}\gamma _{b}\Delta T) = 100 cc.

100 + (V_{1i}\gamma _{i} - V_{1b}\gamma _{b}) \Delta T = 100

V_{1i}\gamma _{i} - V_{1b}\gamma _{b} = 0

\frac{V_{1i}}{V_{1b} }= \frac{\gamma _{b}}{\gamma _{i}}

            =\frac{ 6 \times 10^{-5}}{3.55 \times 10^{-5}}

            =\frac{ 6 }{3.55 }

            =\frac{ 120}{71 }

Now, let V_{1i} = 120x , V_{1b} = 71x

& V_{1i} - V_{1b} = 100

Thus, 120x – 71x = 100

49x = 100

x =\frac{100}{49}

  = 2.04

Thus, V_{1i} = 120 \times 2.04 = 245 cc

V_{1b} = 71 \times 2.04 = 145 cc

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