TEST OF PRACTICAL KNOWLEDGE QUESTION Measure and record the length XY of the resistance wire provided. Connect the circuit shown in the diagram. With R= O\(...

(a) Readings and graph

Length of resistance wire, XY = 100 cm.

Graph of V against I:

Using two widely separated points on the line of best fit, \[ (I_1,V_1)=(0.025\,\text{A},0.50\,\text{V}), \qquad (I_2,V_2)=(0.100\,\text{A},1.75\,\text{V}) \] \[ \text{Slope}=\frac{\Delta V}{\Delta I}=\frac{1.75-0.50}{0.100-0.025}=\frac{1.25}{0.075}=16.7\ \Omega. \] Thus, the resistance of the wire is approximately 16.7 Ω.

Precautions:

1. Connections were clean, tight and correctly made before taking readings.
2. The key was opened immediately after each reading to prevent heating of the resistance wire.

(b)(i)

The experiment is based on Ohm's law. Ohm's law states that the current through a metallic conductor is directly proportional to the potential difference across its ends, provided that temperature and other physical conditions remain constant. Thus,

(b)(ii)

Diameter of wire, \(d=0.2\,\text{mm}=2.0\times10^{-4}\,\text{m}\).

Using \(R=7\,\Omega\), \(\rho=8.8\times10^{-7}\,\Omega\text{m}\), and \(R=\frac{\rho L}{A}\),

Length of the wire = \(0.25\,\text{m}\).