Measurements

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1.general physics  1.1 length and time  -i-Physical Quantity Physical Quantities A physical quantity is a property of an object that can be measured with a measuring instrument. A physical quantity is usually expressed as “a magnitude ( numerical value)  and a  physical unit or more ” Example :- Normal body temperature of a healthy human being is  37  0 C -ii-Length Measuring Length. Length is “the distance between two points in a space”. According to SI units, the length quantity is expressed in meter. There are several kinds of measuring devices used to measure quantity of length, among others, are as follows. Tools used… a-   Measuring tape. b-   Ruler c-   Vernier callipers. d-    Micrometer Measurement of length Length is measured accurately through many meth...
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Thermal properties and temperature

Thermal expansion of solids, liquids and gases 

Solids, liquids and gasses expand when they are heated as the atoms vibrate more and this causes them to become further apart, taking up a greater volume.

Everyday applications and consequences:
-hot water is used to heat up a lid of a jar, to make it expand, so that it is easier to remove
-the liquid in thermometers expand and contract when temperature changes, the volume of the liquid taken up in the tube can be used to find out the temperature
-bimetal thermostat: when the temperature gets too high, the bimetal strip bends, to make contacts separate until the temperature falls enough, then the metal strip will become straight again and the contacts touch, to maintain a steady temperature
-overhead cables have to be slack so that on cold days, when they contract, they don’t snap or detach.
-gaps have to be left in bridge to allow for expansion (rollers allow the bridge to expand)
• “For a fixed mass of gas at constant pressure, the volume is directly proportional to the Kelvin temperature.” •Expansion is highest in gases, then liquids and lowest in solids.

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