Circuits Flashcards
the movement of charge that occurs between two points that have different electrical potentials
current
magnitude of current (I)
I = Q / ∆t
where:
Q = charge passing through conductor
the reciprocal of resistance
conductance
allow current to flow through them
conductive materials
type of conduction:
relies on uniform movement of free electrons in metallic bonds
metallic conduction
type of conduction:
relies on the ion concentration of a solution
electrolytic conduction
materials that do not conduct a current
insulators
charge flows in one direction only
direct current (DC)
charge flow changes direction periodically
alternating current (AC)
two rules that deal with the conservation of charge and energy within a circuit
Kirchoff’s laws
states that the sum of currents directed into a point within a circuit equals the sum of currents directed away from that point
junction rule
junction rule
I (into junction) = I (out of junction)
states that in a closed loop, the sum of voltage sources is always equal to the sum of voltage drops
loop rule
loop rule
V (source) = V (drop)
the opposition to the movement of electrons through a material
resistance
conductive materials with a moderate amount of resistance that slows down electrons without stopping them
resistors
depends on resistivity (ρ), length (L), and cross-sectional area (A) of the material of the resistor
resistance of a resistor (R)
resistance of a resistor (R)
R = ρL / A
where:
ρ = resistivity
L = length
A = cross-sectional area
states that for a given resistance, the magnitude of the current through a resistor is proportional to the voltage drop across the resistor
Ohm’s law
Ohm’s law
V = IR
where:
V = voltage drop
I = current
R = resistance
power (P)
P = W / t = ∆E / t
P = IV = I^2 R = V^2 / R
are additive and sum together to create the total resistance of a circuit
resistors in series
total voltage/resistance of resistors in series
V(s) = V(1) + V(2) + V(3) + … + V(n)
R(s) = R(1) + R(2) + R(3) + … + R(n)
cause a decrease in equivalent resistance of a circuit
resistors in parallel
total voltage/resistance of resistors in parallel
V(p) = V(1) = V(2) = V(3) = … = V(n)
1/R(p) = 1/R(1) = 1/R(2) = 1/R(3) = … = 1/R(n)
have the ability to store and discharge electrical potential energy
capacitors
is determined in parallel plate capacitors by the area of the plates and the distance between the plates
capacitance
capacitance (C)
C = Q / V
where:
Q = charge stores on one plate
V = potential difference (voltage) across capacitor
C = ε(o) A / d where: ε(o) = permittivity of free space (8.85 x 10^-12 F/m) A = area of overlap between plates d = distance between plates
potential energy stored in a capacitor
U = 1/2 CV^2
where:
C = capacitance
V = potential difference (voltage)
cause a decrease in the equivalent capacitance of a circuit
capacitors in series
capacitors in series
1/C(s) = 1/C(1) + 1/C(2) + 1/C(3) + … + 1/C(n)
sum together to create a larger equivalent capacitance
capacitors in parallel
capacitors in parallel
C(p) = C(1) + C(2) + C(3) + … + C(n)
insulators placed between the plates of a capacitor that increase capacitance by a factor equal to the material’s ____ constant (𝜅)
dielectric materials
capacitance with dielectric material
C’ = 𝜅C
where:
C’ = new capacitance with dielectric
𝜅 = dielectric constant
C = original capacitance
are inserted in series in a circuit to measure current; they have negligible resistance
ammeters
are inserted in parallel in a circuit to measure a voltage drop; they have very large resistances
voltmeters
are inserted around a resistive element to measure resistance; they are self-powered and have negligible resistance
Ohmmeters
