Neptune is an average distance of 4.5×10^12m from the sun. estimate the length of the neptunian year.

As per Kepler's third law we know that

now here we know that

= year of Neptune

= year of Earth

= distance of Neptune from Sun

= Distance of Earth from Sun

so now we will have

so length of year of Neptune is 164.3 years

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.