(a) Ohm's Law:
At constant temperature, the potential difference (V) across the ends of a conductor is directly proportional to the current (I) flowing through it.
$$V \propto I \quad \Rightarrow \quad \frac{V}{I} = R \text{ (constant)}$$
(b) The physical quantity determined by the slope of the V–I graph is Resistance (R).
Resistance is defined as the ratio of potential difference across a conductor to the current flowing through it.
$$R = \frac{V}{I} = \text{slope of V–I graph}$$
From the graph (using marked data points, e.g., V = 6 V, I = 2 A):
$$R = \frac{6}{2} = 3 \ \Omega$$
SI unit of resistance is ohm (Ω).
(c) Relationship between 1 kWh and 1 Joule:
$$1 \text{ kWh} = 1 \text{ kW} \times 1 \text{ h}$$
$$= 1000 \text{ W} \times 3600 \text{ s}$$
$$= 3.6 \times 10^6 \text{ W·s}$$
$$\boxed{1 \text{ kWh} = 3.6 \times 10^6 \text{ J}}$$
Source: Chapter 11 – Electricity, Sections 11.2, 11.5, 11.7
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