Two charged thin infinite plane sheets of uniform charge density ${\sigma }_{+}$ and ${\sigma }_{-}$, where $\left|{\sigma }_{+}\right|>\left|{\sigma }_{-}\right|$, intersect at the right angle. Which of the following best represents the electric field lines for the system:

Shown in the figure is a shell made of a conductor. It has inner radius $a$ and outer radius $b$, and carries charge $Q$ . At its centre a dipole $\overrightarrow{\mathit{p}}$ is placed as shown then:

Three charges are placed at the three vertices of an equilateral triangle of side $a$ as shown in the figure. The force experienced by the charge placed at the vertex $A$ in a direction normal to $BC$ is