8.1. A certain magnetic material has the following B-H curve shown in Fig. P8-1: B(MT) 250 TTTTH (KA m' XXXXXXXXXX ] -250 Fig. P8-1. Partial B-H curve for a magnetic material. The magnetic field H is...

8.1. A certain magnetic material has the following B-H curve shown in Fig. P8-1: B(MT) 250 TTTTH (KA m') 250 -250 ] -250 Fig. P8-1. Partial B-H curve for a magnetic material. The magnetic field H is produced by an external coil carrying current. Initially at point /, the material is not magnetized. Then the external field H becomes positive, goes through zero to a peak negative value, and then goes positive again. Various points in this process are numbered as 1, 2, etc. (a) What is the approximate value of the magnetic flux density B in Teslas, T) in the material after the magnetic field H becomes positive and then goes to zero? What is the number designating this point on the curve? (b) Once the material is magnetized so that B is positive, what is the approximate value of negative magnetic field needed to reduce the magnetic flux B to zero? What is the number of this point on the curve? (c) At point 4 on the curve, what is the product of B and H (absolute value)? Express your answer in terms of Jm. In a permanent magnet, this is known as the "maximum energy product" BH max, and is a measure of the ability of the magnet to store magnetic energy.