Term

Definition
R=(L/A)*ρ
R=resistance
L=length (m)
A=cross sectional area (m^{2})
ρ=resistivity of the material (copper 1.62*10^{8} ohm m)
as length and resistivity increase the resistance increases
as the cross sectional area increases the resistance decreases 


Term
relationship between voltage and current in a resistor of constant value 

Definition


Term

Definition
the reciprocal of resistance
units of mhos 


Term

Definition
provides some opposition to the flow of electric current
as current [I(t)] flows through the resistor is produces a voltage drop across the resistor [v(t)], commonly called a voltage drop
relationship btwn voltage drop and the current flow is given by Ohm's law: v(t)=i(t)*R
the voltage drop is proportional to the current flow 


Term

Definition
[image]
R_{T}=R_{1}+R_{2}+R_{3}
I_{T}=V_{1}/R_{T} I_{T}=I_{1}=I_{2}=I_{3}
V_{R1}=I_{T}*R_{1} V_{R2}=I_{T}*R_{2} V_{R3}=I_{T}*R_{3}
V_{T}=V_{R1}+V_{R2}+V_{R3}
C_{EQ}=1/[(1/c_{1})+(1/c_{2})+(1/c_{3})]
L=L_{1}+L_{2}+L_{3}
Kirchoff the sums of the voltage drops around the "loop" must be equal to the applied voltage V1 


Term

Definition
[image]
R_{EQ}=1/[(1/R_{1})+(1/R_{2})]
V1=V_{R1}=V_{R2}
I_{T}=V1/R_{EQ} I_{T}=I_{R1}+I_{R2} Kirchoff sums of the currents through each branch must be equal to the current entering the node from where the branches divide
I_{R1}=V_{R1}/R1 I_{R2}=V_{R2}/R2
C_{T}=C_{1}+C_{2}
L_{EQ}=1/[(1/L_{1})+(1/L_{2})]



Term

Definition
voltage (V)*current (I)
units of watts 


Term

Definition
an energy storage device constructed of 2 conducting plates separated by an insulating (dielectric) material with no electrically conductive connection btwn the plates
stores electrical energy by separating charges (coulombs) such that one plate becomes + and the other 
the separation of charges created by the movement of electrons results in the creation of an electrostatic field. This stores electrical potential energy that can be released back into the circuit whenever it is required
C=(K*A)/d
C=capacitance in farads
K=dielectric constant of the material separating the plates
A=cross sectional area of the plates
d=distance btwn plates 


Term

Definition
a coil of wire that is an electrial energy storage device
an electromagnetic field is produced that is proportional to the magnitude of the current when a current moves thru the wire
electrical energy is stored in the inductor as an electromagnetic field
inductance is physically proportional to the cross sectional area of the coil of wire, number of turns of wire in the coil, and the length of wire making up the coil
units: Henry



Term

Definition
a semiconductor device which only permits current to flow in one direction
conventional current flows in the direction of the arrow on the schematic symbol of the diode
the AC source provides a sine wave signal. while the sine wave is in the positive half of the cycle conventional current flows fromt he plus sign on V1 through the circuit to the other terminal of V1. during the negative half of the cycle, no current will flow bc the positive side of V1 is at the bottom and conventional current can't flow in the reverse direction through the diode 


Term

Definition
device that opens the circuit by interrupting the wire through wich current flows
when the switch is closed the circuit is again complete and the switch acts like an ideal piece of wire (0 resistance) 


Term

Definition
τ=R*C
when a resistor is placed between the battery and the capacitor it limits the maximum current flow and therefore determines how quickly the capacitor becomes charged
as the resistance increases the time required to complete the flow of electrons on to and off of their respective plate's increases 


Term

Definition
X_{c}=1/(2πfC)
f=frequency of the current in Hz
C is the capacitance in Farads
as the frequency increases the capacitive reactance goes down and more current is permitted to flow in the circuit
as capacitance increases so does the current flow if the frequency is held constant
ex: patient on an operating table 


Term

Definition
X_{L}=2πfL
f=frequency in Hz
L is the inductance in Henries
as the frquency increases the inductive reactance increases and less current is permitted to flow
if the inductance increases the reactance increases and the current flow decreases 


Term

Definition
used to describe the opposition to the flow of current in time varying circuits
resistance is a component of impedance, which is also made up of capacitive and inductive reactance
systemic vascular resistance is used as a gross simpification of vascular impedance
Z=√(R^{2})+(X_{L}X_{C})^{2}
also associated with a phase angle that ultimately describes the relationship(time delay) btwn the voltage and the current in the circuit
Φ=tan ((XL/XC)/R 


Term

Definition
device that transfers electrical energy from one circuit to another without a physical connection (wire) btwn them
a changing (alternating) current in the primary, or first circuit, creates a changing magnetic field due to the alternating electrical current flowing thru it; in turn, this magnetic field induces a changing voltage in the secondary or second circuit
V_{s}/V_{p}=N_{s}/N_{p}
V_{s}=secondary induced voltage
V_{p}=primary voltage
N_{s} and N_{p}= number of turns of wire in their respective windings
the power in the primary circuit is approx. equal to the power in the secondary circuit
I_{p}*V_{p}=I_{s}*V_{s}=P_{p}=P_{s} 


Term

Definition
resonant circuits have the ability to selectively amplify certain frequencies and not others
f_{o}=1/(2π√LC)
resonance in the vasculature is responsible for the peripheral arterial pressues having higher systolic pressure than the central pressure waveforms 

