cau 15 :micro dien tu

nguyen ly hoat dong:

-khi  tac dong thanh ap vao phan ung lam cho phan ung dao dong, keo theo su thay doi do rong cua khe tu, lam tu tro bien thien. Tu tro bien thien lam cho tu truong trong long cuon day bien thien, sinh ra sđđ am tan cam ung trong cuon day. 

+ Tu tro cua mach tu:

R(M) ≈(a+x)/(µo*S)      ( nuy o)

trong do: x la do dich cua phan ung khoi vi tri tinh do chiu tac dong cua thanh ap

S: dien tich cua mat cat mach tu tai khe

- khi tu tro thay doi , tu thong do nam cham tao ra cung thay doi theo:

Φ=teta/R(M)

trong do : teta la suc dien dong cua nam cham vinh cuu.

-su bien thien cua tu truong lam xuat hien sđđ cam ung trong cuon day:

E=-W*dΦ/dt=(teta*S*W*µo)*v/(a+x)

=> tu cong thuc tren cho ta thay E phu thuoc vao x: E=f(x): la ham phi tuyen ,nghia la ton tai meo phi tuyen . muon giam meo phi tuyen thi phai thoa man dk x<<a.do do , micro dien tu thuong kem nhay.

cau 16 loa dien tu:

- khi co dong dien am tan chay trong cuon day ,sinh ra tu truong bien thien trong cuon day, tuong ung tao ra luc tu F bien thien. Luc tu F tac dong phan ung dao dong, kick thik am thanh.

+luc tu gay ra dao dong cua phan ung

F=(Φ+Φ~)^2/(2*µo*S)

trong do Φ~ la tu thong bien thien do dong xoay chieu chay trong cuon day sinh ra

Φo la tu thong do nam cham tao ra

- khai trien bieu thuc tren ta thay thanh phan Φ~^2 la song hai bac 2, chung toa ton tai meo phi tuyen

=> de giam nho meo phi tuyen phai thoa man dk Φo>>Φ~ khi do.

F =α*Φo*Φ~ =teta*S*W*µo*i/a^2

tuy nhien thanh phan cuong do tu truong co 1 chi so toi ưu. neu qua lon se lam cho thanh phan khong doi qua lon, do do phan ung ko the dao dong tu do dc.

- he so ghep dien cơ cua he dien tu:

M=teta*S*W*µo* (1/a^2)

=>>loa dien tu chu yeu dc su dung lam ong nghe dien thoai vi re tien

cau 17micro tinh dien:

-khi tac dong len phan dao dong tu do 1 thanh ap dieu hoa thi no se dao dong theo ham mu:

x=x(m)*e^(j*omega*t)

- do khoang cach thay doi lam cho dien dung cua tu cung bien thien: C= εo*S/(a+x)

trong do : εo la hang so dien moi

S dien tich cua tu

a khoang cach tinh giua 2 ban tu

khi dien dung cua tu bien thien , tuong ung xuat hien dong dien chay qua tu:

i=dq/dt=Uo* dC/dt=Uo*( omega khong*S/(a+x)^2)*(j omega *x)≈(Uo*x/a)/(1/jomega Co) =e/Zi

vvoi e =Uo *X/a =Uo*j*omega*x/j omega*a =Uo.v/j omega a: su dao dong cua mang rung ,dich chuyen voi van toc v, se lam suat hien sdd cam ung e o dau ra

He so ghep dien cơ cua he M=Uo/j omega a

cau 18 loa tinh dien

- khi dua dien ap am tan U vao, trong loa xuat hien luc F cam ung. duoi tac dung cua luc tu F lam cho phan ung dao dong , lam cho dien truong giua 2 ban cuc thay doi , lam cho mang loa giua 2 ban cuc cua tu dao dong phat ra am thanh. 

F= (Uo+U~)^2 *  omega khong *S/2a^2= Fo+F~+F2~ 

trrong do

Fo: luc tac dong khi chi co Uo

F~ luc cam ung khi chiu tac dong cua U

F2~: thanh phan hai bac 2 , la thanh phan ko mong muon

trong bieu thuc cua F xuat hien thanh phan hai bac 2 , chung toa ton tai meo phi tuyen

Ta thay: 

F~ =(UoεS/a^2)*U~ = Uo*i/j omega a

=> Chung toa khi co dong am tan o dau vao thi dau ra cua loa xuat hien luc cam ung F

he so ghep dien cơ: M =Uo/j omega a