1. An air-cored coil contains a flux density of 25 mT. When an iron core is inserted the flux density is increased to 1.6 T. Calculate the relative permeability of the iron under these conditions.
2. A magnetic circuit of mean diameter 12 cm has an applied mmf of 275 At. If the resulting flux density is 0.8 T, calculate the relative permeability of the circuit under these conditions.