current electricity Flashcards
inst current
dq/dt
drift velocity
-eEtime(avg)/m
Drft velocity in terms of V
eVt/ml
relationship between I and Vd
I=VdenA
mobility
-et/m=Vd/E
resistivity formula
ml/ne²tA
relationship between T and R for conductors, semi conductors and alloys
cond. - directly proportional
semi cond- inverse
alloys- no effect
resistance and temp coefficient formula
Rf=Ro(1+alphadeltaT)
temperature coefficient is positive for _ and negative for _
cond, semi cond
current density
i=J.A
ohms law vector form
J=Esigma
relation between resistivity and mobility
rho=1/ne(mu)
cells do or do not produce charge
no
terminal voltage is?
Potential difference across two terminals of cell when current is drawn
V=E-Ir
i in terms of internal resistance and emf
i=E/r+R
factors on which r depends (int. R)
area of electrodes (inverse), dist between electrodes (direct), concentration of electrolytes (direct), temperature (direct)
kirchhoffs laws
junction rule and loop rule
power is
Vi
combination of cells in series E and r
E=E1-E2
r=r1+r2
cells combination parallel E and r
E=(E1/r1+E2/r2)/(1/r1+1/r2)
for mixed grouping, equivalent E, r and i are?
En, nr/m, Emn/nr+mR
max power transfer theorem
power transferred to the load is max when ext load resistance becomes equal to equivalent int r
meter bridge formula
unknown R X=(100-l)R/l
potentiometer uses
measuring potential diff, emf of cell, comparing emf, finding int r
principle of potentiometer
potential diff across a wire is directly proportional to length if the wire is of homogeneous material, has uniform cross sec area, constant current flows
formula of V based on potentiometer
V=Kl
where K= irho/area
formula to calculate emf of cell (potentiometer)
E1=(Er/r+R)×l/L
relation between E and l to compare emfa
E directly proportional to l and E1/E2=l1/l2
int resistance formula using shunt
r=(l1-l2)/l2×S
l1>l2
_ velocity determines the current in a conductor
drift
drift velocity is due to
motion of conduction electrons due to electric field
dependence of Vd on E (ohms law)
Vd=E
example of non ohmic resistance
diode
E,J, rho relation
E=Jk
