Ch. 6: Circuits Flashcards
where is metallic conductivity seen
solid metals and some molten salts
where is electrolytic conductivity seen
solutions
unit of conductance
siemens (S)
S/m
what is conductance the reciprocal of
resistance
why are metal atoms good electrical conductors
- easily loose one or more valance electrons
- these electrons then move about in larger collection of metal atoms
what does electrolytic conductivity of a solution depend on
the strength/ion concentration of that solution
equation for current
I = Q / delta t
current = charge passing through conductor / unit of time
unit for current
ampere
A = C/s
relationship between current direction and ion flow
current is SAME direction of proton flow (high to low potential)
current is OPPOSITE direction of electron flow (low to high potential)
direct current flow pattern
charge flows in one direction
alternating current flow pattern
charge flow changes directions periodically
Kirchoff’s Junction Rule
I into junction = I leaving junction
Kirchoff’s Loop Rule
V source = V drop
units of electromotive force (emf)
V = J/C
resistance
opposition within any material to the flow of charge
equation for resistance
R = [p * L] / A
resistance = [resistivity of material * length of material ] / cross sectional area
units of resistivity
p = ohm * meters
effect of temperature on resistance
resistance is usually higher at higher temps
formula for voltage drop between two points
V = IR
equation for actual voltage supplied by a cell
V = E cell - [i * r int]
voltage = emf of the cell - [current through the cell * internal resistance]
equation for power of a resistor
P = IV = I^2 * R = V^2 / R
total resistance of resistors in series
Rs = R1 + R2 + R3 …
total voltage drop for a series of resistors
Vs = V1 + V2 + V3 …
total voltage for parallel resistors
Vp = V1 = V2 + V3 …
total resistance of resistors in parallel
1/Rp = 1/R1 + 1/R2 + 1/R3
OR
Rp = [R1 * R2] / [R1 + R2]
definition of capacitance
ratio of the magnitude of charge stored on one plate to the potential difference (voltage) across the capacitor
equation for capacitance (when voltage is applied)
C = Q / V
unit of capacitance
farad, F
1 F = 1 C/V
equation of capacitance of a capacitor
C = E0 (A/d)
Capacitance = permittivity of free space [area / separation]
equation for uniform electric field established between two plates of a capacitor
E = V/d
equation for potential energy stored within a capacitor
U = 1/2 CV^2
capacitance due to a dielectric material
C’ = kC
total capacitance of capacitors in series
1/Cs = 1/C1 + 1/C2 + 1/C3 …
total capacitance for capacitors in parallel
Cp = C1 + C2 + C3
what do ammeters measure
current
how are ammeters inserted
in series
what do voltmeters measure
voltage drop
how are voltmeters inserted
in parallel
what do ohmmeters measure
resistance
