D. c6ng ciia luc dien trucmg thuc hien khi dich chuy^n eac dien tfch trong
DONG DIEN TRONG KIM LOA
HIEN TLfONG NHIET DIEN. HIEN TLfONG SIEU D A N A - KIEN THL/C LI T H U Y E T C O BAN
HIEN TLfONG NHIET DIEN. HIEN TLfONG SIEU D A N A - KIEN THL/C LI T H U Y E T C O BAN
a) Cac tinh chat dien cua kim loqi
- Kim loai la chat d i n dien tot.
Dien trd suat cua kim loai c6 gia tri rat nho (vao khoang 10 D..m).
- Khi nhiet dp khong d6i, dong dien trong kim loai tuan theo dinh luat 6m.
- Dong dien chay qua day dan kim loai gay ra tac dung nhiet (hieu ufng Jun). - Dien tra suat cua kim loai tang theo nhiet dp.
p, = P o [ l + a ( t - t o ) ]
trong do Po la dien tro suat d IQCQ (thucmg lay la 20°C) ; aVd he so nhiet dien
trd, CO dcfn vi la K '. Ddi vdi mot so kim loai thucmg dung, a c6 tri so vao khoang
10 "^K '. Thi nghiem chinh xac chumg to he so a con phu thupc vao nhiet dp, vao ca dp sach va che dp gia c6ng vat lieụ
b) Thuyet electron tu do trong kim loai
• Trong kim loai, cac nguyfin tu bi mat electron hoa tri trd thanh cac ion
duong. Cac ion duong lien ket voi nhau mot each trat tu tao nen mang tinh the ciia
kim loaị
Chuyen dong nhiet ciia cac ion (dao d6ng ciia ion quanh vi tri can bang) c6 the pha vo trat tir naỵ Nhiet dp cang cao, dao dong nhiet cang manh, mang tinh the cang trd nen mat trat tụ
• Cac electron tach khoi nguyen tu, trd thanh electron tu do, chuyen dong h6n loan trong mang tinh thẹ Cac kim loai khac nhau c6 mat dp electron (so electron tir do trong mot don vi the tich) khac nhau ; mat dp nay c6 gia tri khong doi vdi mPi kim loaị
• Khi dat vao hai dSu vat dan mot hieu dien the, cac electron tu do chiu tac dung ciia lire dien, chuyen dong c6 huong (ngoai chuyen dong nhiet hPn loan) ;