Register for free to see more content

Theory:

This experiment requires a coil of wire, a screw gauge, a metre scale, battery, key, ammeter, voltmeter, rheostat and connecting wires.
2.png
An electric circuit
 
Formula:
R=ρLA
 
Procedure:
• Connect the battery, ammeter, wire, rheostat, and key in series, and the voltmeter in parallel to the unknown resistor.
• Close the key.
• Now, adjust the rheostat such that the ammeter reads a current of \(0.5\ A\).
• Note down the potential difference in the voltmeter.
• Again, adjust the rheostat and change the current in steps of \(0.5\ A\).
• For each current, note the corresponding potential difference in the voltmeter.
• Note down the values.
• Using a screw gauge and a metre scale, measure the diameter of the wire and the length of the coil, respectively.
 
Observations:
(i) To find the resistance:
 
S.No
Ammeter reading- \(I\)
(Ampere)
Voltmeter reading- \(V\) (Volt)
Resistance\(=\) \(\frac {V}{I}\)
(Ohm)
1.   
2.   
3.   
4.   
5.   
6.   
 
(ii) To find the diameter of the wire using screw gauge:
 
S.NoPitch scale reading(PSR) (\(mm\))Head scale coincidence (\(HSC\)) 
Head scale reading
\(HSR\) \(=\) \({HSC } \times {LC}\) (\(mm\))
Total reading \(=\) \(PSR + HSR\) (\(mm\))
1.    
2.    
3.    
 
From the observed data, the resistivity of the material of the wire can be found using the formula.
 
To know more about screw gauge, click here.