Example 7.1 . A thunder was heard 4 s later after the lightning is seen. If the distance of the
lightning is 1396 m away from the observer, what is the speed of sound at
that temperature?

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask

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.