Post office box, principle of balanced Wheatstone bridge. physics practical std 11 & 12 GSEB

Post Office box

POST OFFICE BOX

Aim:-

A post office box and other necessary instruments are given to you. Take three appropriate ratios of the resistances in the two arms of Post Office Box and determine the values of two unknown resistances.

Now connect the unknown resistances in series and parallel respectively and verify the laws of series and parallel combinations of resistances.

PRINCIPLE :-

It works on the principle of balanced Wheatstone bridge.

APPARATUS :-

A Battery,

unknown resistance (Rx & Ry),

Post Office Box,

a galvanometer,

rheostat,

connecting wires

Post office box Apparatus

CONDITION  1 :- 

Connect unknown resistance      Rx between C and D

Post office line diagram condition 1

Post office condition 1 Practical

 CONDITION 2 :- 

Connect unknown resistance      Ry between C and D

 

Post office line diagram condition 2

Post office condition 2 practical

CONDITION 3 :- 

Connect unknown resistance      Rx & Ry in SERIES between C and D

Post office series connection 

Post office series connection practical

CONDITION 4 :- 

Connect unknown resistance      Rx & Ry in PARALLEL between C and D

Post office parallel connection condition 4

Post office box parallel connection 

Post office box observation table

Post office box calculations

Precautions

(1)   All plug keys of Post Office Box must be tight.

(2)    Contact points of K₁ and K₂ must be cleaned  with sand paper.

(3)    Galvanometer should be very sensitive.

(4)    Throughout the experiment  press key K₂(battery key) first and then key K₁(galvanometer key).

For more details view Video.

POST OFFICE BOX

. TO VERIFY THE LAWS OF REFLECTION USING A PLANE MIRROR GSEB Std 8 to 12 Science practical

Reflection of Plain mirror 

Reflection of Plain mirror.

Aim :   To verify the laws of reflection using a plane mirror.

Principle    :  When a ray of light is incident on a reflecting surface, it changes its direction of motion and travels in the original medium following certain laws. This phenomenon is called  reflection of light.

Apparatus : Drawing board, a drawing paper (White), a plane mirror, a foot-rule, a pencil, four pins, four push pins, a protactor, a stand for the plane mirror.

Apparatus : Drawing board, a drawing paper (White), a plane mirror, a foot-rule, a pencil, four pins, four push pins, a protactor, a stand for the plane mirror.

Reflection of Plain mirror Practical

Reflection of Plain mirror

Reflection of Plain mirror

Reflection of Plain mirror

Reflection of Plain mirror

Ø  First of all fix the white drawing paper on the drawing board using push pins.

Ø  First of all fix the white drawing paper on the drawing board using push pins. Place the plane mirror along with its stand and fix its position AB.

Ø  Now draw a line PQ which passes through the mid-point ‘P’ of AB and perpendicular to AB.

Ø  Now draw a line PQ which passes through the mid-point ‘P’ of AB and perpendicular to AB.

Ø  PQ is called the normal to AB.

Ø  Draw a ray RP which makes some angle with the normal (PQ).

Ø  Draw a ray RP which makes some angle with the normal (PQ). On the ray RP fix two pins P₁ and P₂ vertically with 2-3 cm separation between them. Ray RP is incident ray.

Ø  Now from the other side of PQ , (in which incident ray is not there) see the images of pins P₁ and P₂ fix other two pins P₃ and P₄ vertically so that pins P₃, P₄ and images P₁ and P₂ appears collinear at their lower ends.

Ø  Now remove the pins and the mirror. Join the marks of P₃ andP₄ and obtain the reflected ray PS.

Ø  Repeat  the experiment for different angles of incidence. Measure angle of incidence and angle of reflection. Note your reading in the observations table.

Reflection of Plain mirror

Reflection of Plain mirror Observation table

Conclusion : 

Practical uses :  We can study the laws of reflection. We can also study the images obtained by the plane mirror. We can come to know how reflection is used in various optical appliances, e.g., periscope, keleidoscope.

For more details view Video.

Reflection of Plain mirror.

To prepare sulphur dioxide gas in the laboratory Std 8 to 12 Science practical.

Preparation of Sulphur Dioxide in Laboratory

To prepare sulphur dioxide gas in the laboratory. 

AIM :  To prepare sulphur dioxide gas in the laboratory and study its properties.

It is known from the properties of sulphur dioxide that it is extremely pungent smelling colourless bacteriostatic gas. Excess of sulphur dioxide in the air causes air pollution. When it escapes from engine exhaust and factory  chimneys it causes pollution. It is suffocating and leads respiratory inflammation. For this reason it is necessary to reduce  its proportion from the air.

THEORY :  Copper metal and concentrated sulphuric acid reacts to give corresponding  acid salt ( copper sulphate ) and sulphur dioxide gas.

APPARATUS  : Round bottom flask, thistle funnel, delivery tube, four to five gas jars, stand, two-holed cork, lid, wire gauze, tripod stand, etc.

CHEMICALS  : Copper metal, Sulphuric acid, red and blue litmus papers, wax, potassium permanganate, magnesium strip etc.

Preparation of Sulphur dioxide in Laboratory

Observation :- 

Physical properties :

1. Colour of sulphur dioxide gas :
2.  Odour or small of sulphur dioxide gas:
3.  Solubility of the gas in water :
4.  During the experiment this gas is collected by the upward displacement of air, therefore this gas is                    than air.

Chemical properties :

1. When red and blue litmus papers are inserted in gas jar containing sulphur dioxide.
2.  When an ignited magnesium ribbon is held in a gas jar containing sulphur dioxide.
3.  When potassium permanganate solution is added to the gas jar containing sulphur dioxide.
4.  Give the chemical reaction, which is used to prepare sulphur dioxide in laboratory.

CONCLUSION :-

PRACTICAL USES

It is known from the properties of sulphur dioxide that it is extremely pungent smelling colourless bacteriostatic gas. Excess of sulphur dioxide in the air causes air pollution. When it escapes from engine exhaust and factory  chimneys it causes pollution. It is suffocating and leads respiratory inflammation. For this reason it is necessary to reduce  its proportion from the air.

For more details View Video:

To prepare sulphur dioxide gas in the laboratory. 

To test the presence of Carbon monoxide and Sulphur dioxide in the atmosphere. Biology std 11 & 12

To test the presence of Carbon monoxide and Sulphur dioxide in the atmosphere.

Test of Carbon  and Sulphur dioxide

INSTRUMENTS
Filter paper,  
Palladium or Platinum chloride, Acidic potasium dichromate.
Test for Carbon monoxide
Filter paper deep in chemical
Keep where transportation is more and smoke of automobiles is very high
View the changes on filter paper.
Slowly slowly it gets change in colour.
After some times 
Finally you see the change in colour that is due to Carbon monoxide is presence in Air.

Test for Sulphur dioxide
Filter paper deep in chemical
Keep where transportation is more and smoke of automobiles is very high
View the changes on filter paper.
Slowly slowly it gets change in colour.
After some times 

Finally you see the change in colour that is due to Sulphur dioxide  is presence in Air.

For more details view Video

To test the presence of Carbon monoxide and Sulphur dioxide in the atmosphere.

Angle of deviation of GLASS PRISM, GBSE practical for std 11 & 12.

Angle of Deviation of Glass Prism

ANGLE OF DEVIATION OF GLASS PRISM, 

12.1  AIM :-

Determine with the help of pins, the angle of the given glass prism. Determine the values of angle of emergence and angle of deviation for four different values of angle of incidence. Hence prove that  i + e = A +d.

PRINCIPLE : Reflection and refraction of light.

APPARATUS:  Glass Prism, Drawing paper, Drawing board, Pencil, Ruler, Pin, Protector,

PRECAUTIONS

Ø    While marking the position of a prism with pencil, the prism should not be disturbed.

Ø   A prism should be carefully put back exactly at the marked position.

Ø    While pressing the heads of the pins for fixing them use metal coin or a hard object so that you do not hurt your palm.

Ø    Do not press the pins very hard in the board otherwise it becomes difficult to remove them afterwards.

Ø   See that the pins pushed in the board remain perpendicular to the board.

PROCEDURE :

Take paper and pin it on Drawing board. 

Now take Glass prism and put it on center of Drawing board paper.

Mark the edges of the prism with pencil.

Angle of Deviation of Glass Prism Practical

Draw line P₁ M perpendicular  to prism base BC.

Insert two pins vertically P₁ & P_2..

Place the Prism on its original position.

NOTE :- Pins should be 3 – 4 cm. away from each other.

Observe pins from the side AB and insert two pins P’₁ & P’₂ such that images of P₁ ,P₂ and pins P’₁ & P’₂ are collinear.

Angle of Deviation of Glass Prism Procedure

Draw line Q₁ N perpendicular  to prism base BC

Insert two pins verticallyQ₁ & Q_2.

Angle of Deviation of Glass Prism Procedure

Place the prism on its original position

Observe pins from the side AC and insert two pins Q’₁ & Q’₂ such that images of Q₁ ,Q₂ and pins Q’₁ & Q’₂ are collinear.

Angle of Deviation of Glass Prism Procedure

Measure angle with protector ÐP’₁OQ’_1.

Angle of PRISM = ÐP’₁OQ’₁  / 2.

Angle of Deviation of Glass Prism Procedure

For more details view Video

Angle of Prism:

pH value of solution and fruit juices GSEB std 8 to 12 Science

ph Value of Fruit juice

To determine the pH value of solution and fruit juices with the use of pH-paper approximately.

AIM  : To determine the pH value of solution and fruit juices with the use of pH-paper approximately

APPARATUS   : Seven glass  test tubes, one dropper, Test tube stand, and glass rod. Dilute hydrochloric acid solution,Lemon juice, Tomato juice, Distilled water, Sodium chloride solution, Sodium hydroxide solution, Sodium carbonate solution,

THEORY  :  [ The pH scale runs from 0 to 14 ]

If the pH of a solution is 7 it is a neutral solution. pH of acid is less then seven and that of base is more than seven.

Thus the nature of solution whether neutral, acidic or basic can be known by knowing by pH value of  solution. In the school laboratory pH value is determined by using pH papers. The basic principle of the pH paper is that it undergoes a suitable change in colour which is characteristic of the pH of the test sample of the solution. In this way pH paper is an indicator in different media of solutions giving different colour.

In the laboratory red and blue litmus papers are also used to find pH value less than 7 pH, more than7pH and 7pH.

pH value of solution and fruit juices

ph value of Dilute hydrochloric acid

pH value of solution and fruit juices

ph vales of Sodium chloride solution

ph vales of different Fruit juice

ph values table 

CONCLUSION

PRACTICAL USES : From pH value the property of substance or solution whether acidic, neutral or basic can be determined.

Change in Chemical reactions Exothermic OR Endothermic GSEB Science 8 to 12

Exothermic reaction 

To measure the change in chemical reactions and conclude whether the reaction is exothermic or endothermic.

AIM  : To measure the change in chemical reactions and conclude whether the reaction is exothermic or endothermic.

THEORY  :  During the chemical reaction if the temperature increases the reaction is exothermic and if temperature decreases the reaction is endothermic.

APPARATUS  : Conical flask, 250 ml Beaker, Stand, Thermometer,  Glass rod, measuring cylinder, stirrer.

Exothermic Reaction (step 1)

Exothermic Reaction (step 2)

Exothermic Reaction (step 3)

MATERIAL       :  Dilute hydrochloric acid, Zinc metal, Solid ammonium chloride,

Observation

(1) initial temperature of dilute hydrochloric acid              ⁰ C.

(2) Temperature of the mixture when Zinc metal dissolves in    hydrochloric acid =         ⁰ C.

(3) Difference of temperature =                    ⁰ C.

(4) Give chemical reaction of Zinc metal with hydrochloric acid.

NOTE     :  (1)  Similarly heat of neutralization in neutralization reaction between                      dilute hydrochloric acid and sodium hydroxide can be measured.

                   (2)  The increase in temperature can be noted when dissolution of solid                    sodium hydroxide in water is carried out.

PRACTICAL USES

The combustion reactions of kerosene, Petrol, LPG are exothermic, therefore these substance are used as fuel.

Endothermic Reaction :

Endothermic reaction (step 1)

Endothermic reaction (step 2)

Endothermic reaction (step 3)

Observation

(1) Initial temperature of water =         ⁰ C.

(2) Temperature o ammonium chloride solution when dissolved in        water    =              ⁰ C.

(3) Difference between temperatures  =                    ⁰ C.

NOTE  :   *    Similarly when Sodium nitrite is dissolved in water decrease in              temperature occurs.

PRACTICAL USES

Some substances absorb heat from atmosphere, during the reaction therefore used to reduce the temperature.