6. A brass ring with triangular cross section encircles a very long straight wire

concentrically as in Figure 7.2. If the wire carries a current I, show that the total number

of magnetic flux lines in the ring is

2mb [b-ana+b

4 =

Calculate if a = 30 cm, b = 10 cm, h = 5 cm, and I = 10 A.

Brass ring

Figure 2.- Cross section of a brass ring enclosing a long straight wire; for Problem 6