Determine the diameters dA and dB (i) and evaluate r = ((dA)/(dB))2 (ii).

To determine the diameters $d_A$ and $d_B$, a micrometer screw gauge is used to measure the thickness of each wire. Multiple readings should be taken at different points along each wire, and the average value calculated to minimize error. Once $d_A$ and $d_B$ are obtained, the ratio $r$ is calculated using the formula:

Since no experimental data for diameters is provided, numerical values for $d_A$, $d_B$, and $r$ cannot be determined here.

Steps (iii) through (xi) describe the experimental procedure. This involves setting up the circuit for wire A as shown in Fig. 3(a), closing the key, and adjusting the rheostat to obtain various current ($I_A$) and corresponding voltage ($V_A$) readings. This process is then repeated for wire B, using the circuit in Fig. 3(b), to obtain $I_B$ and $V_B$ readings.

The collected current and voltage readings for both wires A and B should be organized into a table. A suitable table structure is:

Plot the values of $V_A$ on the vertical (y) axis against the corresponding values of $I_A$ on the horizontal (x) axis. Draw the best-fit straight line through the plotted points. For an ohmic conductor, this graph will be a straight line passing through the origin.

The slope $S_A$ of the $V_A$ versus $I_A$ graph represents the resistance of wire A ($R_A$). To determine the slope, select two distinct points $(I_{A1}, V_{A1})$ and $(I_{A2}, V_{A2})$ on the best-fit line and calculate:

The unit of the slope will be Ohms ($\Omega$). Without the graph, a numerical value for $S_A$ cannot be provided.

On the same axes used for wire A, plot the values of $V_B$ on the vertical (y) axis against the corresponding values of $I_B$ on the horizontal (x) axis. Draw the best-fit straight line through these points. This line represents the V-I characteristic for wire B, and its slope will give the resistance of wire B ($R_B$).