Measure and record the length XY of the resistance wire provided.
Connect the circuit shown in the diagram.
With R= O\(\Omega\), close the key, K. Read and record the current \(1_o\) and the voltage drop \(V_o\) across the resistance wire.
Setting R = 1\(\Omega\). close the key. Read and record the current, I, and the corresponding voltage drop, V across the wire.
Repeat the procedure for five other values of R= 5, 10, 20, 40, and 60\(\Omega\). Tabulate your readings.
Plot a graph of V on the vertical axis against 1 on the horizontal axis.
Determine the slope of the graph
State two precautions taken to ensure accurate results.
(b)i. Mention and state the law on which the experiment in (a) is based.
ii. A piece of resistance vire of diameter 0.2 mm and resistance m has a resistivity of 8.8 x 10\(^{-7}\)\(\Omega\)m, calculate the length of the Wire. [\(\pi\) =\(\frac{22}{7}\)]
Verified Correct Answer: .
Physical Principles & Numerical Solution
Table of values
XY = 100cm
R(\(\Omega\))
1(amp)
V
0
0.15
2.65
1
0.15
2.65
5
0.15
2.65
10
0.10
1.85
20
0.08
1.40
40
0.06
0.90
60
0.04
0.70
Slope = \(\frac{x_{2}-x_{1}}{y_{2}-y_{1}} = \frac{1.75-0.5}{0.10-0.025} = \frac{1.25}{0.075}\)
Precautions:
I ensured good contact and the correct connection of the circuit.
I avoided incorrect positioning of the eye (error due to parallax).
Open the key plug when recording the reading taken.
(b)i. The experiment is based on Ohm's law. Ohm's law states that the current flowing through a metallic conductor is proportional to the potential difference between its ends provided the temperature and other physical conditions of the conductor remain constant; i.e: \(\frac{V}{|}\) = Constant.
ii. Area of cross-section of wire = \(\frac{\pi d^{2}}{4} = \frac{\frac{22}{7} \times (0.2)^{2}}{4}\)
\(\frac{3.143 \times 0.04}{4}\) = 0.031mm\(^{2}\) = 3.1m\(^{2}\)
Resistivity = \(\frac{RA}{L}\), length (L) = \(\frac{R.A}{resistivity}\)
= \(\frac{7 \times 3.1}{8.8 \times 10^{-7}} = \frac{21.7}{8.8 \times 10^{-7}}\) = 2.47 x 10\(^{-7}\)
Source: Myschool Past Questions Archive (Record #60111)