Heat flows from body at high temperature to low temperature.

The temperature of the body measured by the thermometer.the branch is Thermometry, heat.

Fundamental interval=Upper fixed point- lower fixed point.

Upper fixed point – pure water exposed to 1-atmosphere pressure boils 100°C.                                          Lower fixed point- pure ice exposed to 1-atmosphere pressure melts 0°C

Individual temperature converting from one scale to another scale

100\C=180\F-32=100\K-273 =80\R

Temperature difference converting from one scale to another scale



Pyrometer: Infrared sensitive devices used to detect infrared radiation. The triple point of water- 273.16 k.        Material resistivity insensitive to temperature is Nichrome. The temperature of the sun determined by Pyrometer.                 At constant volume gas thermometer works on Charles law.

Fractional increase in resistivity per unit increase in temperature is Temperature co- efficient resistivity.


1)At what temperature of a body, its temperature measured in °C or °F coincide?

Sol: Let °C =°F =x                                     5\C=9\F-32                                        5\x=9\x-32                                            9x=5x-160                                           4x=-160                                                  x=-40

2)what is the temperature for which the readings of kelvin & Farenhiet scales are same?

Sol: Let K=F=x=?                                             5\K-273=9\F-32                                        5\x-273=9\x-32                                        5x-160=9x-2457                                 -4x=-2457+160                              -4x=-2297                                         X=-4\-2297                                      X=574.25

3) Temperature of a body increased from 32°R to 373K.find change in temperature of body in °C,°F,Kelvin&Raemer scales??

Sol: t1=32°R

5\C=4\R.                  5\K-273\=5\C.    5\C=4\32.        Cancel 5 both side    5\C=1\8.                   373-273=C.        C=40°C.                  100°C=t2.                t1=40°C.

∆t=t2-t1.                                                ∆t=100-40=60°C.                              9\∆F=5\∆C.      5\∆K=5\∆C  9\∆F=5\60.       ∆K=60°C.                    ∆F=108°F.

4\∆R=5\∆C.                                           4\∆R=5\60.                                         ∆R=48R

Imp formula:

Principle of thermometrs             U.F.P-L.F.P\Reading shown by any temp-L.F.P=CONSTANT

4)For a faulty centigrade thermometer L.F.P is at -40°C &U.F.P  at 102°C.if this m\t measure temperature of a body is 49°C.find?

a)Correct temperature of the body.

b)Error in the reading shown& necessary correction?

Sol:                   √                    ×                        L.F.P.   0°C.            -4°C.                      U.F.P   100°C          102°C.                        Rs.        ?                 49°C.        (U.F.P-L.F.P\Rs-L.F.P)√=(U.F.P-L.F.P\Rs-L.F.P)x

Rs= Reading shown by any temp

(100-0\Rs-0)√=(102-(-4)\49-(-4). )×      ( 100\Rs)√=(106\53)×                  Rs√=2\100=50

Error=xmeasured value-xtrue value

= 49C-50°C=-1°C


Also read Maths tricks for fast calculation


Its also about heat


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