Circuits Flashcards
What is current?
considered the flow of positive charge
What is the unit for conductivity?
Siemens (S) or Siemens/meter
Metallic Conductivity relies on …..
the uniform movement of free electrons in metallic bonds
Electrolytic Conductivity relies on ….
the ion concentration of a solution
What is the equation for current?
I = Q/deltat Q = charge
What is the unit for current?
ampere (1 A = 1 C/s)
Direct Current vs Alternating Current
DC - charge flows in one direction only
AC - charge changes direction periodically
What is electromotive force?
“pressure to move” - the voltage when there are no charges moving between the two terminals
What is Kirchhoff’s two rules?
Junction Rule and Loop Rule
What is Kirchhoff’s Junction Rule?
at any point or junction in a circuit, the sum of currents directed into that point equals the sum of current directed away from the point
Current(into junction) = Current(leaving junction)
What is Kirchhoff’s Loop Rule?
Around any closed circuit loop, the sum of voltage sources will always be equal to the sum of voltage (potential) drops
V(source) = V(drop)
What is voltage?
the potential difference between two points
What is the unit for voltage?
volts (J/C)
What is conductivity?
reciprocal of resistance; measure of permissiveness to current flow
The conductivity in ______ solutions is always lower than in _____ solutions.
nonionic;ionic
What is resistance?
the opposition within any material to the movement and flow of charge
What is the equation for the resistance of a resistor?
R = pL/A R = resistance p = resistivity L = length of the resistor A = cross-sectional area
What is resistivity and its units?
p - intrinsic resistance to current flow in a material
units = ohm-meter
If a resistor’s cross-sectional area is doubled, its resistance will be cut in ______.
half
What are conduction pathways?
the number of pathways that current can flow through the resistor - the wider the resistor, the more pathways
What is Ohm’s Law?
V = IR V = voltage drop I = current R = magnitude of the resistance in ohms
Equation for actual voltage of a cell
V = Ecell - ir(int)
r(int) - internal resistance of the cell
Ecell = emf of the cell
i = current through the cell
What is the equation for power in relation to current?
P = IV I = current V = voltage
Series vs Parallel
Series - which all current must pass sequentially through each resistor connected in linear arrangement
Parallel - which the current will divide to pass through resistors separately
What is equivalent/resultant resistance?
the sum of all the individual resistances of resistors that are in series
What is the equation for calculating resistance in parallel?
I/Rtotal = 1/R1 + 1/R2 + … + 1/Rn
The total resistance is _____ by wiring two identical resistors in parallel.
halved
What are capacitors?
devices that can hold charge at a particular voltage
What is the equation and units for capacitance?
C = Q/V Q = charge V = voltage Units = farad (1 F = 1 C/V)
What is the equation for capacitance of a parallel plate?
C = E0*(A/d) E0 = 8.85 x 10 -12 F/m A = area of overlap of the two plates d = separation of the two plates
What is the potential energy in a capacitor?
U = 1/2CV^2
What is a dielectric material?
an insulator
What is a dielectric constant?
(k) - measure of its insulating ability
What is the equation with capacitance due to a dielectric material?
C' = kC C' = new capacitance with the dielectric present k = dielectric constant C = old capacitance
What is the equation for the equivalent capacitance for capacitors in series?
1/Ctot = 1/C1 + 1/C2 + … + 1/Cn
What is the equation for the equivalent capacitance for capacitors in parallel?
Ctot = C1 + C2 + … + Cn
What are ammeters?
used to measure the current at some point within the circuit
What is a voltmeter?
measure voltage drop across two points in a circuit
What is an ohmmeter?
measure resistance
