The diameter of a wire ST varies linearly with distance along the wire as shown in Fig. 6.1. [Figure 6.1] There is a current I in the wire. At end S of the wire, the diameter is d and the average drift speed of the free electrons is vₛ. At end T of the wire, the diameter is 2d.

1. (a)Define the coulomb.[1]
2. (b)An electric current is a flow of charge carriers. In the following list, underline the possible charges for a charge carrier. 8.0 x 10⁻¹⁹ C 4.0 x 10⁻¹⁹ C 1.6 x 10⁻¹⁹ C 1.6 x 10⁻²⁰ C[1]
3. (c)On Fig. 6.2, sketch a graph to show the variation of the average drift speed with position along the wire between S and T. [Figure 6.2][2]

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