C. 4,35Q d 2,175n
Bad toain thuaih coutheanoo't giau quyeil: nho sau:
0oi v&i moi nhanh tu' cua m9ch tu, c6 the xem tu cam Ctng tu' B la khong doi tren toan b9 chieu dai cua nhanh d6, ta xac dinh gia tri c- cJng d9 tu tr- cJng H t- ong Ctng dy'a tren quan h$
B = µ.H. (4.11)
Trang h$ do I- cJng SI:
- B d-(Jc do bang weber/m2 hay con d-(Jc g9i la tesla (T),
- µ d-(Jc do bang weber/A hoific (H/m).
Tu thEim cua sat tu' d-(Jc bieu dien bang µ = µr - µ0 v&i gia tri pho bien cua µr cua cac v$t li$u tu' dung de che t90 cac thiet bi di$n nam trang khoang tu' 2000 den
80000, hoific dy'a tren quan h$ d- cJng cong tu' h6a cua v$t li$u cho tr- &c.
Tfch giU'a c- cJng d9 tu' tr- cJng va chieu dai nhanh tu chf nh la gia tri sCtc tu' d9ng
can thiet Fi = Hi Ii .
SCtc tu' d9ng can thiet cua toan b9 m9ch tu' se bang tong cac sCtc tu' d9ng nhanh nam trong m9t m9ch vong khep kf n.
(4.12)
D9ng bai toan co ban thCt hai th- cJng kh6 giai hon. 0e nh$n d-(Jc tu' thong sinh ra tu sCtc tu d9ng cho tr- &c, c6 the c6 the thy'c hi$n bai toan theo ph- ong phap 1$p nh- sau: dau tien ta ch9n m9t each tuy y, m9t so gia tri tu' thong <I>, sau d6 theo each giai bai toan thu$n ta xac dinh d-(JC cac gia tri t- ong Ctng cua sue tu' d9ng. Ket qua nh$n d-(Jc cho phep xay dy'ng d- cJng bieu dien quan h$:
<I> = f(Fi ), tu' d6 Ctng v&i sCtc tu' d9ng ban dau de cho ta tra ra gia tri tu' thong
can thiet.