$$ \text { In the following circuit, the terminal voltage across the cell is } $$

Two cells of emfs $E_1$ and $E_2$ and internal resistances $r_1$ and $r_2\left(E_2>E_1\right.$ and $\left.r_2>r_1\right)$ respectively, are connected in parallel as shown in figure. The equivalent emf of the combination is $\mathrm{E}_{\text {eq. }}$. Then

The variations of resistivity $\rho$ with absolute temperature T for three different materials $\mathrm{X}, \mathrm{Y}$ and Z are shown in the graph below. Identify the materials $\mathrm{X}, \mathrm{Y}$ and Z .

Given, a current carrying wire of non-uniform cross-section, which of the following is constant throughout the length of wire?