Chapter 6: Circuits Flashcards
current (I)
the amount of charge passing through the conductor per unit time
Q / delta T
(the flow of positive charge
flows from a positive terminal to negative terminal
metallic conductivity
current flows through metals atoms
electrolytic conductivity
current flows through ionic solution
conductivity
a measure of permissiveness to current flow; measure in siemens
reciprical to resistance
SI unit for conductance
siemens
current units
coulombs / sec = ampere (A)
1 A = 1 C/s
direct current
current flows in one continuous direction
alternating current
current which periodically reverses direction and changes its magnitude continuously with time
voltage (potential difference)
electromotive force (emf)
the potential difference of the voltage source for a circuit, usually a battery
given in volts
voltage units
1 V = 1 J/C
Kirchhoff’s Junction Rule
Kirchhoff’s Loop Rule (?)
V source = V drop
resistance
the opposition within any material to the moment and flow of charge
a measure of the opposition to current flow in an electrical circuit
conductors
materials that offer almost no resistance to current flow
insulators
materials that offer very high resistance to current flow
resistors
conductive materials that offer amounts of resistance between conductors and insulators
more conductive than insulators, less conductive than conductors
regulate current flow
characteristics that affect resistance of a resistor
resistivity, length, cross-sectional area, and temperature
resistance equation
R = ρL/A
ρ = resistivity, L = length, A = cross-sectional area
resistivity (ρ)
the number that characterizers the intrinsic resistance to current flow in a material (constant for a given material and temperature)
resistance and length
positive linear relationship
doubled length = doubled resistance
cross-sectional area
inverse linear relationship
cross-sectional area doubled = resistance halved
conduction pathways
a route for current to take through a resistor
a wider resistor has more conduction pathways within
temperature and resistance
most conductors have higher resistance at higher temperatures
hot wire = more resistance
Ohm’s Law equation
V = IR
V = voltage drog
I = current
R = magnitude of resistance
current flows from ____ to ____
current flows from positively charge, high potential to negatively charged, low potential
secondary batteries
can be recharged
out outside source provides voltage to the positive end of the battery
Power of resistor
rate at which the resistor dissipates energy from the circuit (to another form of energy, ex. heat or light)
P = IV = I^2R = V^2/R
equivalent / resultant resistances (series)
the sum of the individual resistances
equivalent resistance (resistors in parallel)
RP will always decrease as more resistors are added
capacitor
an electronic component that stores electrostatic energy in an electric field
a device that stores electrical energy (charge?) by putting positive charges on one plate and negative charges on another plate, creating an electric field
uses 2 metal plates separated by an insulator and stores electrical charge by pumping electrons from one side to another
capacitor type covered on the MCAT
parallel plate capacitor
capacitance equation
C = Q/V
Q = the magnitude of the charge stores on one plate
V = the voltage across the capacitor
SI unit for capacitance
farad
1 F = 1 coulomb / volt
capacitance of a parallel plate capacitor
uniform electric field equation
E = V/d
capacitor function
to store an amount of energy in the form of charge separation at a particular voltage
potential energy store in a capacitor
U = ½ CV^2
dielectric material
synonymous with insulator
dielectric materials ____ (increase/decrease) the capacitance of the capacitor
dielectric materials increase the capacitance of the capacitor
dielectric constant (K)
a measure of a given materials insulating ability
a vacuum has a dielectric constant of 1
capacitance due to a dielectric material
C’ = kC
C’ = the new capacitance with the dielectric present
C = the original capacitance
equivalent capacitance _______ (increases/decreases) as more capacitors are added in series
decreases
resultant capacitance of capacitors in parallel…
is equal to the sum of the individual capacitances
meters
the devices used to measure circuit quantities (current, voltage, resistance, capacitance) in the real world
ammeters
used to measure the current at some point within a circuit
(“am” → amp)
require a circuit to be active
voltmeters
creates an alternate pathway for the current in order to measure the voltage drop from the 2 points where it connects to the original circuit
have very high resistance so not many electrons take this alternate path
require a circuit to be active
ohmmeters
does NOT require a circuit to be active
the meter measures the current, and then uses the known voltage and Ohm’s law to determine resistance
