Variation in electric potential is maximum if one goes

If $V$ is the electric potential at a given point,then the electric field $E_x$ in the $x$-direction at that point is:

The electric potential $V$ at any point $(x, y, z)$ (all in metres) in space is given by $V = 4x^2 \text{ volt}$. The electric field at the point $(1 \text{ m}, 0, 2 \text{ m})$ in $\text{volt/metre}$ is

The electrostatic potential inside a charged spherical ball is given by $V = b - ar^2$,where $r$ is the distance from the centre; $a$ and $b$ are constants. Then,the charge density inside the ball is:

What is the potential gradient in a wire of resistivity $40 \times 10^{-8} \, \Omega \, m$ and cross-sectional area $8 \times 10^{-6} \, m^2$ when a current of $0.2 \, A$ flows through it?

Electric field at a point $(x, y, z)$ is represented by $\vec E = 2x\hat i + y^2\hat j$. If the potential at $(0, 0, 0)$ is $2 \, V$,find the potential at $(1, 1, 1)$. (in $/3$)