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

Ohm's law physics practical for ITI fitter & GSEB Std 8 & 12

Ohm's Law 

Ohm's Law

AIM :-

A voltmeter, a current meter, and an unknown resistance etc. are given to you. Prepare an appropriate circuit to verify Ohm’s law. With  appropriate values of current and voltages, only with the help of calculations, determine  the value of unknown resistance.

PRINCIPLE

Potential difference in a conductor produces electric current.

APPARATUS :-

A unknown resistance,

a voltmeter (0 - 10 V),

a milliammeter (0 - 500mA), a battery,

a rheostat,

a tap key,

connecting wires.

PRECAUTIONS : -

1. All the connections must be tight.
2. Plastic or rubber should not be pressed below the connecting terminals.
3. When current does not flow in a circuit the pointer in both ammeter and voltmeter must be on zero. If it is not so then adjust the pointer on zero or consider the zero error.
4. Range of the meters must be appropriate.
5. Choose a proper scale while plotting the graph so that the graph is sufficiently large and it occupies most part of the graph-paper.

Ohm's Law apparatus

Ohm's law Line diagram

Ohm's law line diagram 

Ohm's law practical

Ohm's law observation table

Ohm's law graph

For more details View Video.

Ohm's Law

TANGENT GALVANOMETER, Physics practical std 11 & 12 GSEB

Tangent Galvanometer

TANGENT GALVANOMETER, 

AIM :

To determine the value of H with the help of a tangent galvanometer.

APPARATUS :

A tangent galvanometer, an ammeter, a battery, a simple key, a rheostat, a reversible key and a spirit level.

PRECAUTIONS

1)      Keep the tangent galvanometer away from an ammeter.

2)       The circular platform must be properly leveled horizontally.

3)       Before taking the reading of the pointer of a tangent galvanometer, the sight should be so adjusted that the pointer and its image in the mirror, become collinear.

4)       The rheostat should be so adjusted that the deflection is between 30⁰ and 60⁰.

5)       The coil of the tangent galvanometer should be adjusted parallel to the magnetic field of the earth.

Apparatus for Tangent Galvanometer Practical

Line Digram for Tangent Galvanometer

Insert Key.

Tangent Galvanometer Procedure

Connect reversible key and adjust rheostat.

Note down reading of Tangent Galvanometer, and ammeter.

Tangent Galvanometer Procedure

Connect  key in reverse position and adjust rheostat.