Micrometer screw gauge, ITI fitter, std 8 t0 12

Micrometer (Screw Gauge) 

Screw gauge or micrometer screw gauge is a measuring instrument used for precision measurement.  

Micrometr : Frame

Frame : Made up of Dropped Forged steel or Malleable Steel. All other parts joint with frame. 

Micrometer (Screw Gauge)  : Anvil

Anvil : Most important parts of Micrometer, which is made up of Alloy steel, hardening, tempering and finishing is done very accurately. 

Micrometer (Screw Gauge) : Spindle

Spindle : Is made up of Nickel Chrome metal, which is also hardened, Grind and accurately made. Which is move to and fro as we rotate thimble. The maximum displacement of spindle is 25 mm.

Micrometer (Screw Gauge) : Measuring Faces

Measuring Faces : Both the end of Anvil and Spindle, Measuring face is fixed, which is made from Alloy steel, as well as hardened, grind and accurately finished. 

Micrometer (Screw Gauge) : Barrel or Sleeve

Barrel or Sleeve : The Barrel or sleeve is connects the frame to the cylindrical tube. It is a non-movable part of the screw gauge and has a scale inscribed over it which is the main scale of the device. Moreover, it also carries the most important part of the micrometer- the screw. 

Micrometer (Screw Gauge) : Thimble

Thimble: The thimble or head is the end of the cylindrical tube and is turned to move and adjust the spindle. The thimble carries the Micrometer or secondary scale. 

Micrometer ( Screw Gauge) : Ratchet

Ratchet : There is one more part called the ratchet which is provided at the end of the tube. The ratchet is kind of limiting device which applies a pressure by slipping at a predetermined torque and thus prevents the spindle from moving further. 

Micrometer (Screw Gauge) : Lock nut

Lock Nut : screw gauges also consist of locking devices which holds the scales at a particular position for prevent any kind of error while taking readings.

Before you use any micrometer you should know the Least count .

Pitch = distance travelled by thimble on linear scale in one rotation.

Metals, Non-Metals and Carbon, std 8 to 12 CBSE GSEB

Metals, Non-Metals and Carbon .
Revision of properties of metals and non-metals.
Carbon .
Occurrence, allotropes of carbon (diamond, graphite, coal etc.).
Reason of allotropy, physical and chemical properties of carbon.
Uses.
Properties and uses of calcium carbide.
Properties and uses of silicon carbide.
Carbonates and bicarbonates.

Tests. Sodium bicarbonate and sodium carbonate. 

Historical aspects of metals.
1. Pre-historic man used weapons made of stones, bones and horns for his living. Later on he started using weapons made of metals.
2. Egyptians started using gold for the first time around 14th century B. C.
3. During the period of early civilization (around 3500 B.C.) articles made of copper and tin were being used.
4. Period around 2500 B. C. was called Bronze age.
5. Asians around 200 B. C. and Chinese around 900-500 B.C. were using Iron.
6. Iron pillar near Qutubminar in Delhi was installed in 4th century B. C. Even today its rust-free grandeur is un-paralled.

Metals and Non-metals.
Many materials that we use in our daily life such as glass, cement, vessels, ornaments, electrical equipments, paper, paints, perfumes, medicines, synthetic fibers etc., are made of the naturally occurring 90 elements, their compounds and their mixture.
You have studied in previous chapters about some elements and the compounds.
Elements are classified as metals and non-metals based on certain general properties. About 80% elements are metals !

Activity :
Make a list of metallic and non metallic substances that are used in your home. Write their uses. 

Properties of metals and non-metals. 
In the previous classes, you have studied the general properties of metals and non-metals. Let us review some of them once again.
Note : 
Element with highest atomic number (92) is Uranium. two elements having atomic number less than 92 are not occurring in nature. 
They are Technician and Astatine. 

Chemical properties of Metals and Non-metals

Note:
Elements which have the intermediate properties (i.e., between metals and non metals ) are called Metalloids.
Eg. : Germanium, Arsenic.

Know the meanings
Acidic oxides
Basic oxides
Covalent compounds
Oxidising agents
Reducing agents 

Elements
Metals 
+O2
Basic oxides
+H2O
bases 

Non-Metals
+O2
Acidic oxide
+H2O
acids

Experiment 7.1
Take 2-3 pieces of zinc in a test tube. Add a little quantity of dilute sulphuric acid to it. Tie a balloon to the mouth of the test tube immediately. Observe the small bubbles rising in the acid and the balloon becoming bigger.
Reason it out.

Activity 7.2 
Try to cut sodium using a knife. 

Tell your experience and conclusion.
Caution : Sodium is highly reactive element. Touching it with bare hands is dangerous.

Activity 7.3
Beat a piece of tin several times with a hammer. 

Tell the changes that occur in its shape. 

Which property does it exhibit ?