To determine the resistance per cm. of given wire by plotting a graph of potential difference versus current | Physics Practical Class 12 | Gaurav Kumar

 To determine the resistance per cm. of given wire by plotting a graph of potential difference versus current.

Aim: -

To determine the resistance per cm. of given wire by plotting a graph of potential difference versus current.

APPARATUS: -

About 100 cm of high resistivity wire, a battery eliminator or dry cell a d. c. voltmeter (0-3V), a d. c. ammeter (0-3A) a rheostat, a plug key, connecting wires, meter scale, sand paper.

THEORY: -

OBSERVATIONS: -

1.    Range of instrument  Ammeter                         =   ........... A 

2.    Least count of Ammeter                                     =    ........... A

3.    Zero Error of Ammeter                                       =  nil

4.    Range of instrument Voltmeter                           =    ............. V

5.    Least count of Voltmeter                                     =     .......... V

6.    Zero Error of Voltmeter                                       =    nil

OBSERVATION TABLE

Mean value of resistance, R = .......................... ohms.

7.    Length of the resistance wire l = .......... cm.

CALCULATIONS: -

PRECAUTIONS: -

1.    The voltmeter should be connected in parallel and ammeter in series and these should be so connected that the current enter at the positive terminal and leaves at the negative terminal.

2.    Before plugging in the key, ensure that circuit and connections are tight.

3.    The plug should be inserted only while taking observations, otherwise current would  cause unnecessary heating in the circuit.

4.    Measuring instruments of appropriate range should be used and zero error in them if any must be taken in to account.

5.    Too high currents should not be drawn from the battery and short circuiting must be avoided.

6.    The unknown resistance chosen should have high values in comparison with internal resistances of the cell used.

7.    The length of the resistance wire measured should be that between one terminal of voltmeter to the other. The length at ends wound around the terminals of voltmeter is included would give error in measured length.

RESULT: -

1.    Graph between potential drop 'V' and the current through the3 conductor 'I' is a straight line.

2.    The resistance of the given wire is ........... ohm.

3.    The resistance per cm of the given wire is ........ ohm per cm.