An electric current flows along an insulated strip `PQ` of a metallic conductor. The current density in the strip varies as shown in the graph. Which one of the following statement could explain this variation?

Options

A. The strip is narrower at `P` than at `Q`
B. The strip in narrower at `Q` and at `P`
C. The potential gradient along the strip is uniform
D. The resistance per unit length of the strip is constant

Answer

A

Explanation

(a) The current density at `P` is higher than at `Q`. For the same current flowing through the metallic conductor `PQ`, the cross-sectional area at `P` is narrower than at `Q`. The resistance per unit length `r`is given by `r = (rho)/(A)`
Where `rho` is the resistivity and `A` is the cross-sectional area of the conductor `PQ`. Thus, `r` is inversely proportional to the cross-sectional area `A` of the conductor.