You are provided with a potentiometer x y; a jockey, J; a standard resistor, R, and other necessary apparatus.
(b)i) Explain what is meant by the potential difference between two points in an electric circuit.
ii. A piece of resistance wire of diameter 0.2m and resistance 7\(\Omega\) has a resistivity of 8.8 x 10\(^{-7}\) \(\Omega\)m. Calculate the length of the wire. [\(\pi\) = \(\frac{22}{7}\)].
Table of values/observation
l\(_{o}\) = 0.8A
| S/N | L(cm) | l(A) | (L\(^{-1}\)cm\(^{-1}\)) |
| 1 | 25.0 | 1.20 | 0.040 |
| 2 | 40.0 | 1.00 | 0.025 |
| 3 | 55.0 | 0.95 | 0.018 |
| 4 | 70.0 | 0.85 | 0.014 |
| 5 | 85.0 | 0.8 | 0.012 |
When 1\(^{-1}\) =0, l = 0.66A
\(\frac{|_{o}}{|} = \frac{0.8}{0.66}\) = 1.212
Precautions:
(b) The p.d between two points is the work done (in joules) in moving an electric charge of one coulomb across the two points.
ii. R = \(\frac{PL}{A} = \frac{4pL}{\pi d^{2}}\)
d = 0.2m, \(\pi\) = \(\frac{22}{7}\), R = 7\(\Omega\), p = 8.8 x 10\(^{-7} \pi \), L = ?
\(\therefore\) 7 = \(\frac{4 \times 8.8 \times 10^{-7} \times L}{\frac{22}{7} \times (0.2)^{2}}\)
7 = \(\frac{4 \times 8.8 \times 10^{-7} \times L \times 7}{22 \times 0.04} = \frac{28 \times 8.8 \times 10^{-7} \times L}{0.88}\)
L = \(\frac{7 \times 0.88}{28 \times 8.8 \times 10^{-7}}\)
L = \(\frac{6.16}{246.4}\) x 10\(^{-7}\)
L = 0.025 x 10\(^{7}\)
L = 2.5 x 10\(^{-2}\) x 10\(^{7}\)
L = 2.5 x 10\(^{5}\)
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