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Thermal Properties of Matter physics ncert solutions class 11th Physics Class 11th Physics NCERT Exemplar Solutions Class 11th Chapter Eleven

We would like to prepare a scale whose length does not change with temperature. It is proposed to prepare a unit scale of this type whose length remains, say 10 cm. We can use a bimetallic strip made of brass and iron each of different length whose length (both components) would change in such a way that difference between their lengths remain constant. If 5 α_iron=1.2 $\times$ 10^-5/K and α_brass 1.8 $\times$ 10^-5 /K , what should we take as length of each strip?

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Payal Gupta | Contributor-Level 10

4 months ago

This is a long answer type question as classified in NCERT Exemplar

As l_iron-l_brass=10cm= constant at all temperature

Let l_o be the length of temperature at 0⁰C and l be the length after change in temperature

l_iron-l_brass=10cm

l_iron (1+ $α_{i r o n} ? t$ )-l_brass (1+ $α_{b r a s s} ? t$ )=10cm

I_{iron
$α$}_iron= I_{brass
$α$}_brass

$\frac{l_{i r o n}}{l_{b r a s s}}$ =1.8/1.2=3/2

$\frac{1}{2} l_{b r a s s} = 10 c m$

L_brass=20cm and l_iron=30cm

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A glass full of hot milk is poured on the table. It begins to cool gradually. Which of the following is correct?

(a) The rate of cooling is constant till milk attains the temperature of the surrounding

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This is a multiple choice answer as classified in NCERT Exemplar

(b), (c), (d) When the hot milk in the table is transferred to the surroundings by conduction, convection and radiation.

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Refer to the plot of temperature versus time (Fig) showing the changes in the state of ice on heating (not to scale) Which of the following is correct?

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(a), (d) During the process AB temperature of the system is 0⁰C . hence it represents phase change that is transformation of ice into water while temperature remains 0⁰C.

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