Some students are planning an experiment. They need to be able to vary the strength of a magnet. Which type of magnet should they use? A. bar magnet B. electromagnet C. horseshoe magnet D. refrigerator magnet​

Consider an insulating crystal, made up of layers of atoms. what form would you expect the temperature dependence of the phonon heat capacity to approach at extremely low temperatures if the interlayer coupling is i)very strong (rigid coupling), and ii) very weak. explain.