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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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(b) The temperature of milk falls off exponentially with time

(c) While cooling, there is a flow of heat from milk to the surrounding as well as from surrounding to the milk but the net flow of heat is from milk to the surrounding and that is why it cools

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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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