Maharashtra Board Solutions for Chapter: Magnetic Fields due to Electric Current, Exercise 2: Use your brain power

We have seen that in case of parallel conducting wires carrying steady currents, the Biot-Savart law and the Lorentz force law give the result in Eq. ${\mathrm{F}}_{21}=-{\mathrm{F}}_{12}$. Is this consistent with Newton's third law? (Consider for example the gravitational pull experienced by the Earth towards the Sun and that by the Sun towards the Earth.) 

Using electrostatic analogue, obtain the magnetic field at a distance $x$ on the perpendicular bisector of a magnetic dipole 

$\overrightarrow{\mathrm{m}}$ .For $\mathrm{x}\gg \mathrm{R}\text{, verify that }\overrightarrow{\mathrm{B}}=\frac{{\mathrm{\mu }}_0}{4\mathrm{\pi }}\frac{\mathrm{m}}{{\mathrm{x}}^3}$

What is the fundamental difference between an electric dipole and a magnetic dipole? 

By making different choices for the Amperian loop, show that $B = 0$ for points outside an ideal toroid. What must be ideal toroid?