Measure and record the emf, \(V_o\) of the cell provided.
Connect a circuit as shown in the diagram above.
With the key, K closed vary the rheostat, Rh to obtain a current 1 = 0.20A. Read and record the corresponding value of the potential difference, V on the voltmeter.
Evaluate 1\(^{-1}\) and V\(^{-1}\).
Repeat the procedure for four other values of l = 0.25, 0.30, 0.35 and 0.40 A. Tabulate your readings.
Plot a graph V\(^{-1}\) on the vertical axis against 1\(^{-1}\) on the horizontal axis.
Determine the slope, s, of the graph
Evaluate s\(^{-1}\).
State two precautions taken to ensure accurate results.
(b)i. Explain Ohmic conductor:
ii. Explain resistivity of the material of a wire.
Verified Correct Answer: .
Physical Principles & Numerical Solution
1. \(v_o\) = 3.0v
2. \(V_R\) = 0.20 volts
3. l = 0.20, 1\(^{-1}\) = \(\frac{1}{1} = \frac{1}{0.2}\) = 5
V = 0.2, V\(^{-1}\) = \(\frac{1}{V} =\frac{1}{0.2}\) = 5
Table of values/observations
S/N
IA
I\(^{-1}\)(A\(^{-1}\))
V(volts)
V\(^{-1}\)(volts\(^{-1}\))
1
0.20
5.00
0.19
5.26
2
0.25
4.00
0.23
4.35
3
0.30
3.33
0.28
3.57
4
0.35
2.86
0.33
3.03
5
0.40
2.50
0..38
2.63
Slope (s) = \(\frac{\bigtriangleup {V}^{-1}}{\bigtriangleup {I}^{-1}}\)
S = \(\frac{5.1-1.0}{4.55-12} = \frac{4.1}{3.35}\) = 1.224
S\(^{-1}\) = \(\frac{1}{s} = \frac{1}{1.224}\) = 0.817
N.B: R = S\(^{-1}\) = 1.0
Precautions taken to ensure accurate results are as follows
Tight connections ensured/clean terminals
Repeated readings have been shown on the table
Parallax error in reading voltmeter/ammeter avoided
Key open when reading is not being taken
(b)i. An ohmic conductor is s Conductor in which the current passing through it is proportional to the p.d across the conductor, provided temperature and other physical conditions are constant.
ii. The resistivity of the material of a wire is the resistance of a unit length of the wire of unit Crofs sectional area. It is denoted by p. and measured in ohm-metre (L-m).
Source: Myschool Past Questions Archive (Record #60081)