Losses in a magnetic recording head Consider eddy current losses in a permalloy magnetic head for audio recording up to 10 kHz. We will use Equation 8.50 for the eddy current losses. Consider a magnetic head weighing 30 g and made from a permalloy with density 8.8 g cm3 and resistivity 6 107 m. The head is to operate at Bm of 0.5 T. If the eddy current losses are not to exceed 1 mW, estimate the thickness of laminations needed