Formule iz Osnova Elektrotehnike (I dio) koje se mogu koristiti na meduispitima

ε0 = 8.854 · 10−12 As

V m

εr =ε

ε0

F =Q1Q2

4πεd2~E =

~F

Q

E =σ

εE =

Q

4πεr2

ϕA =Wp

Q

ϕ(x) = −E · x+ ϕ0

UAB = ϕA − ϕB

A12 = W1 −W2 = QU12

C =Q

UC = ε

S

d

WC =QU

2=Q2

2C=CU2

2

I =Q

t

J = NQv J = κE =I

S

R =U

I=

1G

R = ρl

SG = κ

S

l

Rϑ = R20[1 + α(ϑ− 20

W = I2Rt

P = UI = I2R =U2

R−−−−−−−−−−−−−−−−−Ruk = R1 +R2 + . . .+Rn (ser.)

1Ruk

=1R1

+1R2

+ . . .1Rn

(par.)

1Cuk

=1C1

+1C2

+ . . .1Cn

(ser.)

Cuk = C1 + C2 + . . .+ Cn (par.)

niz∑j=1

Uiz =nR∑k=1

Rk · Ik (petlja)

U = Ik. Ri

ηnaponski =Rt

Rt +Riηstrujni =

Ri

Rt +Ri

R1 ·R3 = R2 ·R4

(mosni spoj)

transformacija: trokut −→ zvijezda

R1 =R12R31

(R12 +R23 +R31)

R2 =R23R12

(R12 +R23 +R31)

R3 =R31R23

(R12 +R23 +R31)

transformacija: zvijezda −→ trokut

R12 = R1 +R2 +R1R2

R3

R23 = R2 +R3 +R2R3

R1

R31 = R3 +R1 +R3R1

R2

µ0 = 4π · 10−7 V s

Am

~F = Q(~v × ~B)

~F = I(~l × ~B) |~F | = IlB sin(α)

B = µ0I

2πr Φ = ~B~S = BS cos(α)

ui = Blv eind = −N dΦdt

= −Ldidt

L = NΦI

M12 = N2Φ12

I1

M = k√L1L2 eM = −M di

dt

uL(t) = Ldi(t)dt

uM (t) = Mdi(t)dt

WL =LI2

2−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−

Ief =Im√

2Uef =

Um√2

f =1T

ω = 2πf

a = b+ jc = Aejα = A 6 α

b = Re{a} = A cosα

c = Im = A sinα

A =√b2 + c2

u(t) = Um sin (ωt+ α)

u = Umej(ωt+α)

Um = Umejα U = Uejα = U̇

u(t) = Im{u}

XL = ωL BL =1ωL

XC =1

ωCBC = ωC

Z R ± jX ϕ = arctan( )

Y = G ∓ jB ψ = arctan(B)

ϕ = −ψ

−−−−−−−−−−−−−−−−−

Frekvencijske karakteristike:Im{Z} = 0 Im{Y } = 0

ω0 =1√LC

serija RLC:

Z(ω) =√R2 + (ωL− 1

ωC)2

ϕ(ω) = arctanωL− 1

ωC

R

ρ =

√L

C

paralela RLC:

Y (ω) =√

(1R

)2 + (ωC − 1ωL

)2

ψ(ω) = arctanωC − 1

ωL

γ1

=

paralela RL i RC:

ω0 =1√LC

√√√√R2L −

LC

R2C −

LC

1R

−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−

{a}

k =Φ12

Φ1

2

ind

=ρ

R

|~F | = sin(α)Q Bv

1

n∑j=1

Ij = 0 (c̆vor)

n∑j=1

j =0U

∑=

∑I I

izlu

p.h. s.

U=E d·

|~F | =1

µ0I2· I1· l

2π d

QS =QPγ

−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−

−−−−−−−−−−−−−−−−−=Umcos(ωt+α) Umsin(ωt+α)+j

=

=GG

G

)]

XR R

=Umsin(ωt+α)

U6 α=