Tag: application of various thermometric scales

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

Name the device for detecting and measuring small amount of thermal energy.

  1. Pyranometer

  2. Pyrometer

  3. Barrater

  4. Bolometer
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A bolometer is a device used for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance.

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

State whether true or false :
A gas thermometer measures temperature with the variation in pressure or volume of a gas.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A gas thermometer measures temperature by the variation in volume or pressure of a gas.This thermometer functions by Charles's Law. Charles's Law states that when the temperature of a gas increases, so does the volume.

Using Charles's Law, the temperature can be measured by knowing the volume of gas at a certain temperature by using the formula, written below. Translating it to the correct levels of the device that is holding the gas. This works on the same principle as mercury thermometers.

${\displaystyle V\propto T\,},$
or

${\displaystyle {\dfrac {V}{T}}=k} $
T is the temperature.

V is the volume.

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

  1. $300^\circ C$

  2. $30^\circ C$

  3. $3000^\circ C$

  4. $300 \ K$
Reveal answer Fill a bubble to check yourself
A Correct answer
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,

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

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

$\implies T _H=300^0 C$


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

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 ${ \gamma  } _{ a }=121\times { 10 }^{ -5 }{ { \circ  } _{ C } }^{ -1 }$

  1. 0.96 gm

  2. 0.9 gm

  3. 1 gm

  4. 2 gm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The overflow volume is given by V * deltaT * (gamma_liquid - gamma_glass). Assuming the weight thermometer expansion is negligible or included in the effective coefficient, the overflow mass is m * deltaT * gamma_alcohol. 45 * (33-15) * 121 * 10^-5 = 45 * 18 * 0.00121 = 0.9801 gm, which rounds to 1 gm.

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

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.

  1. $6.0$

  2. $2.5$

  3. $0.5$

  4. $0.4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Increase in length of each liquid is same 

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

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

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

  1. $1.04Kcal$

  2. $10.4Kcal$

  3. $104Kcal$

  4. $1040Kcal$
Reveal answer Fill a bubble to check yourself
C Correct answer
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 $=104\ kcal$
Multiple choice physics heat - measurement application of various thermometric scales different types of thermometers measuring temperature introduction to temperature

Which of the following statements is correct?

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.