select a device that uses energy and explain its energy source its efficiency and where energy might be lost according to the law of conservation of energy

low freq = 100 mhz

low wavelength =101.7m

length = 3x10^8/freq

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.