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

MEASUREMENT OF RESISTANCE ( WHEATSTONE’S BRIDGE) gseb std 11 & 12 physics practical.

Wheatstone's bridge

MEASUREMENT OF RESISTANCE

            ( WHEATSTONE’S BRIDGE)

Condition (1) :- MEASUREMENT OF RESISTANCE

AIM :-

You are given a Wheatstone bridge and other necessary instruments. Find the values of the unknown resistance Rx. Exchange the positions of unknown resistance and resistance box in the gaps of Wheatstone bridge and repeat the experiment.

PRINCIPLE :-

It works on the principle of balanced Wheatstone bridge.

Apparatus :-

Wheatstone-bridge (meter-bridge),

2 Volt Battery,

Rheostat,

Galvanometer,          

Jockey,

Key,

Resistance box(1 – 100  W),

Resistance coil.

Precautions

1. Make proper and tight connections.
2. Keep the keys tightly closed in the resistance box.
3. Adjust the value of resistance box so that null point is obtained between 40 cm and 60 cm.
4. Do not slide the jokey continuously over the wire. 

Note :-  Keep high resistance of rheostat in the beginning of each observation so that current is less and the galvanometer is not damaged. After getting approximate position of null point only decrease the resistance of rheostat.

Wheatstone's bridge Appartatus

Wheatstone's bridge Practical

Wheatstone's bridge

Wheatstone's bridge Observation table

Wheatstone Bridge    ( Line Diagram )

(2)  Condition :- Interchange unknown resistance R_x between  P – Q.

Wheatstones bridge appartatus

Wheatstone's bridge practical

Wheatstones bridge observation table

Wheatstosnes bridge conclusion

For more details view Video

MEASUREMENT OF RESISTANCE

            ( WHEATSTONE’S BRIDGE)

LAWS OF COMBINATION OF RESISTORS ( WHEATSTONE’S BRIDGE & POST OFFICE BOX ) Physics practical gseb std 11 & 12

Wheatstone's bridge

 LAWS OF COMBINATION OF RESISTORS

( WHEATSTONE’S BRIDGE & POST OFFICE BOX )

Experiment :- 3.1

AIM :-

You are given a Wheatstone Bridge and other necessary instruments.

Find the values of the unknown resistance Rx and Ry .

Now connect them in series and parallel respectively and measure their resultant resistances and test the laws of series and parallel connections.

PRINCIPLE :-

It works on the  principle of a balanced Wheatstone bridge.

Apparatus :-

Wheatstone-bridge (meter-bridge),

2 Volt Battery,

Rheostat,

Galvanometer, 

Jockey,

Key,

Resistance box(1 – 100  W),

Resistance coil.

Precautions

(1)   Make all connections tight.

(2)    Clean the ends of the connecting wire with a sand paper.

(3)    Plug keys of resistance box should be very tight.

(4)     Adjust the value of R from the resistance box such that null-point is obtained between 40 cm. and 60 cm.

Laws of combination of resistors

Wheatstone's bridge Apparatus

Wheatstone's bridge Line Diagram

Wheatstone's bridge Practical

Wheatstone's bridge Observation table

(2)   Condition :-

Connect unknown resistance R_y between  M – N.

 

Wheatstone's bridge Line diagram

Wheatstone's bridge line diagram

Wheatstone's bridge Practical

Wheatstone's bridge observation table 2

 (3)   Condition :-

Connect unknown resistance Rx & Ry in Series.

 

Wheatstone's bridge series connection condition 3

Wheatstone's bridge condition 3 Line diagram 

wheatstone's bridge practical

Wheatstones bridge observation table condition 3

(4) Condition :-

Connect unknown resistance in Parallel .

Wheatstones bridge parallel connection

Wheatstones bridge parallel connection practical

wheatstones connection conclusion

Find resistance of two resistors series and parallel, std 8 to 12 GSEB

Effective resistance of two resistor practical

To find effective resistance of two resistors connected in (1) Series (2) Parallel connection.

(ohm’s Law)

AIM : To find effective resistance of two resistors connected in (1) Series (2) Parallel connection.

PRINCIPLE  :  When two resistors are connected in series effective resistance is equal to the sum of their resistance. When two resistors are connected in parallel connection reciprocal of effective resistance is equal to the sum of reciprocal of the resistance.

APPARATUS  :   Ammeter ( 0 – 500 mA), Voltmeter ( 0 -10 V ),  Battery eliminator ( 0 – 12 V), Two unknown  resistors, Plug-key, rheostat, wires,

Find Resistance of Resistor Practical

Find Resistance of Resistor Practical

SERIES CONNECTION

Find Resistance of Resistor Practical

PARALLEL CONNECTION

Find Resistance of Resistor Practical

Observation table of Resistor practical

CONCLUSION

(1) Average value of resistance  R₁ =             W          

(2) Average value of resistance  R₂ =         W

(3) Average value of effective resistance in series connection R₃ =     W

(4) Average value of effective resistance in parallel connection R₄ =     W        

Note : Verify :    (1) R₃ = R₁ + R₂ for series connection.

                               (2) 1/ R₄ = 1/ R₁ + 1/R₂ for parallel connection

PRACTICAL USES

Many times resistance are connected in series e.g. series of small bulbs used for decoration. Domestic connections are always in parallel, e.g. bulbs, tube-light, t.v., fridge. Etc.