Minggu, 07 November 2010

Thermometer

The definition of thermometer and temperature.

Thermometer is a tool to measure temperature of an object

Temperature is the degree of hotness and coldness of an object

A thermometer consists of :

1.A long glass tube has scale

2.Capillary pipe

3.Liquid ( mercury or alcohol )

4.The upper part is vacuum

Kinds of thermometer

There are four kinds of thermometer based on the scale :

1.Celcius scale thermometer : 0oC-100oC

2.Reamur scale thermometer : 0oR-80oR

3.Fahrenheit scale thermometer : 32oF-

212oF

4.Kelvin scale thermometer : 273oK-

373oK

To Compare scales of thermometer

C : R : F = 100 : 80 : 180

C : R : F = 5 : 4 : 9

The equation used to convert the scale:

C scale to R scale : T0R=4/5T0C

R scale to C scale : T0C = 5/4 T0R

C scale to F scale : ToF = 9/5 ToC + 32

F scale to C scale : ToC= 5/9 ( ToF – 32 )

C scale to K scale : ToK = ToC + 273

The liquids are use as a thermometer filler is :

Mercury and Alcohol

The weaknesses of mercury

1. Its price is very high

2. It cannot measure very low temperature ,because its freezing point is – 40oC

3. Mercury is poisonous

The Superiorities of Mercury

1.It is visible , because its silvery shining

2.Its expansion is regular

3.It can measure a high temperature

4.It does not make wet the wall of its

place .

5.It can measure the temperature quickly

and precisely

The weaknesses of alcohol

It cannot measure a high temperature.

It makes wet the wall of its place

It is colourless

The Superiorities of alcohol

It can measure a low temperature.

It can measure the temperature precisely

Its expansions is regular

The upper fixed point of

Celsius,Reamur,Fahrenheit and Kelvin thermometer is the temperature of boiling water

The lower fixed point of

Celsius thermometer is the temperature of melting ice.

Fahrenheit thermometer is the temperature of the mixture of ice and salt

EXERCISE

1. The temperature of matter measured by Reamur thermometer is 60o. If it is measured by Celsius Thermometer its temperature becomes……..

2. The temperature of a body measured by Celsius thermometer is -40o. If it is measured by Fahrenheit Thermometer, its temperature becomes……..

3 .What is temperature ?

4 . The temperature of an object is 27oC

What is the temperature when it is

measured in Kelvin?

5 . The temperature of an object is 400ºK

What is the temperature when it is

measured in Celsius?