Tag: measuring temperature

Questions Related to measuring temperature

The resistance of a platinum wire of a platinum resistance thermometer at the ice point is $5 \Omega$ and at steam point is $5.4 \Omega$. When the thermometer is inserted in a hot bath, the resistance of the platinum wire is $6.2 \Omega$. Find the temperature of the hot bath.

physics heat - measurement application of various thermometric scales different types of thermometers measuring temperature introduction to temperature

  1. $300^\circ C$

  2. $30^\circ C$

  3. $3000^\circ C$

  4. $300 \ K$

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Correct Option: A
Explanation:
Given,

Resistance of platinum wire at ice point, $R _0=5\,\Omega$

Resistance of platinum wire at hot bath $R _H=6.2\,\Omega$

Temperature at hot bath $T _H=?$

We have,

$R _T=R _0[1+\alpha(T-T _0)]$

$\implies R _{100}=R _0[1+\alpha(T _{100}-T _0)]$

$\implies 5.4=5[1+\alpha(100-0)]$

$\implies \dfrac{5.4}{5}-1=100\alpha$

$\implies \alpha=\dfrac{1}{1250}  \, ^0 C^{-1}$

Also,

$R _H=R _0[1+\alpha (T _H-T _0)]$

That is,

$6.2=5[1+\dfrac{1}{1250}(T _H-0)]$

$\dfrac{6.2}{5}-1=\dfrac{1}{1250}\times T _H$

$\implies T _H=300^0 C$


A thermometer uses 

physics heat - measurement application of various thermometric scales different types of thermometers measuring temperature introduction to temperature

  1. water

  2. mercury

  3. air

  4. none

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Correct Option: B

45 gm of alcohol are needed to completely fill up a weight thermometer at $15^{\circ}C$. Find the weight of alcohol which will overflow when the weight thermometer is heated to $33^{circ}C$.
(Given ${ \gamma  } _{ a }=121\times { 10 }^{ -5 }{ { \circ  } _{ C } }^{ -1 }$

physics heat - measurement application of various thermometric scales different types of thermometers measuring temperature introduction to temperature

  1. 0.96 gm

  2. 0.9 gm

  3. 1 gm

  4. 2 gm

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Correct Option: C

Consider two thermometers $T _1$ and $T _2$ of equal length which can be used to measure temperature over the range $\theta _1$ and $\theta _2$. $T _1$ contains mercury as thermometric liquid while $T _2$ contains bromine. The volumes of the two liquids are the same at the temperature $\theta _1$. The volumetric coefficients of expansion of mercury and bromine are $18\times 10^{-5}K^{-1}$ and $108\times 10^{-5}K^{-1}$, respectively. The increase in length of each liquid is the same for the same increase in temperature. If the diameters of the capillary tubes if the two thermometers are $d _1$ and $d _2$ respectively, then the ratio $d _1:d _2$ would be closest to.

physics heat - measurement application of various thermometric scales different types of thermometers measuring temperature introduction to temperature

  1. $6.0$

  2. $2.5$

  3. $0.5$

  4. $0.4$

Show answer
Correct Option: D
Explanation:

Increase in length of each liquid is same 

$\dfrac{\Delta V _{hg}}{\pi d _1^2}=\dfrac{\Delta V _{br}}{\pi d _2^2}$
$\dfrac{\Delta V _{hg}\Delta\theta}{\pi d _1^2}=\dfrac{\Delta V _{br}\Delta\theta}{\pi d _2^2}$
$\dfrac{d _12}{d _2^2}=\dfrac{\gamma _{hg}}{\gamma _{br}}=\dfrac{1}{6}$
$\dfrac{d _1}{d _2}=0.4$

$\begin{array} { l } { \text { Energy required to dissociate } 4 \mathrm { g } \text { of gaseous } } \ { \text { hydrogen into free gaseous atoms is } 208 \mathrm { Kcal {at}  }  } \ {  25 ^ { \circ } \mathrm { C } \text { . The bond energy of } \mathrm { H } - \mathrm { H } \text { bond will be : } } \end{array}$ .

physics heat - measurement application of various thermometric scales different types of thermometers measuring temperature introduction to temperature

  1. $1.04Kcal$

  2. $10.4Kcal$

  3. $104Kcal$

  4. $1040Kcal$

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Correct Option: C
Explanation:
Given heat of atmosphere $40=260\ Kcal$
$2H _{2} \rightarrow 4H$
$\triangle H = 208\ Kcal$
$20 \rightarrow 1\ mole$
$40 \rightarrow 2 \ mole$
$Hene \ 2 H-H$ bonds area brown $bg $
$20\ kcal $ energy so in order to break $1\ H-H$ bound we required $\dfrac{208}{2}= 104\ Kcal$
Hence the bond energy of $H-H$ bound will be $=104\ kcal$

Which of the following statements is correct?

physics heat - measurement application of various thermometric scales different types of thermometers measuring temperature introduction to temperature

  1. Air escaping from a punctured tyre feels cold

  2. When a gas under high pressure is permitted to expand into a region of low pressure, it gains in temperature

  3. The reading on a thermometer immersed in boiling water varies as the heat increases or decreases above the boiling point

  4. None of the above statements is correct

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Correct Option: A
Explanation:

Option (A) is correct. 

Reason - The air is contained at high pressure in the tube. When it escapes through a small hole, it suddenly expands. A large amount of heat is absorbed in the process of expansion resulting in considerable fall in its temperature. This is why the escaping air feels cold.