

Explanation
(a)


Description: The circuit is set up as shown above. The key (k) is closed. The rheostat (R) is adjusted so that lowest current is flowing. Ammeter and voltmeter readings (I and V) are recorded. Adjust rheostat to increase current. Ammeter and voltmeter readings are recorded for other positions of the rheostat. Values of (are plotted against values of I. Slope, which is the value of the resistance is determine.
Precautions;
i) Kcy should be removed when readings are not taken
ii) Connections should be tight
(iii) Parallax' error when reading ammeter and voltmeter should be avoided
(iv) Only low current should be used
v) Zero error of the meters should be avoided. Note: Any correct two) Resistance, R = P'/A where = length of wire, A = cross sectional area, p = resistivity )f wire. But slope, S of graph = R. Hence S = P'/A
Measure I with a metre rule. Measure diameter with a micrometer screw gauge and determine A. Substitute p = \(\frac{SA}{I}\)

c) Diagram

i) Total e.m.f. = 4V
Total resistance = 1 + 2 + \(\frac{3 \times 3}{ 2 \times 3}\)
= 3 + 1\(\frac{1}{2}\)
= \(\frac{1}{2} \Omega\)
E = IR\(_T\),
= E/R
:.Current, I = 4/9 x 2/1
= 8/9;
A = 0.9A

(ii) P.d = IR = 8/9 x 3/2 = 4/3 = 1.3V
(iii) Lost volts = Ir = \(\frac{8}{9}\) x 1 = \(\frac{8}{9} = 0.9V\)


