Problem Sheet 8

The numbers in square brackets refer to the number of the problem in your textbook.

1. [E15.4] A magnetic element has two unpaired electrons and an exchange interaction that causes them to align such that their magnetic fields are parallel. Its atomic volume , $\Omega$, is 3.7 x 10-29 m3. What would you expect its saturation magnetization, Ms, to be?
2. [E15.5] A coil of turns and length 10 mm carries a current of 0.01 amps. The core of the coil is made of a material with a susceptibility $\chi = 10^4$. What is the magnetization M and the induction B?
3. A transformer core is wound with a coil carrying an alternating current at a frequency of 50 Hz. Assuming the magnetization to be uniform throughout the core volume of 0.01 m3, calculate the hysteresis loss. The hysteresis loop has an area of 60000 units, when the axes are drawn in units of 10-4 Wb m-2 and 102 A m-1.
4. In a 440 V, 50 Hz transformer, the total iron loss is 2300 W. When the applied voltage is 220 V at 25 Hz, the total iron loss is 750 W. What is the contribution of the eddy current losses in both these cases? What is the hysteresis loss at 50 Hz?
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