Electricity Flashcards
What is a circuit?
Collection of elements or a collection of elements and signals that are connected together for purposes of modifying input signals to obtain other desired responses
In a circuit picture of a battery, which is the + positive side of the battery?
The long bar
What is the type of amplifier used in physiology?
Differential Amp (Type 2)
What kind of circuit does not allow for work ?
Short circuit
What is the definition of an electric current?
The flow of charges per unit time
What is the unit of charge?
Coulomb
What is the MKS unit of electric current?
Ampere
How much does 1 ampere represent?
Flow of one Coulomb per second
How much does a negative coulomb equal?
6.25 x 10^18 electrons
How is voltage measured?
Always between 2 points
What is V = IR
Ohm’s Law
voltage = current x resistance
What is Darcy’s law?
Q = P / R
What is the difference signal and flow signal of electrical measurements?
DS : Voltage V (volts)
FS : Current I (amperes)
What is the difference signal and flow signal of hydraulic measurements?
DS : pressure P (dynes / cm^2)
FS : flow V (cm^3 / sec)
What is the difference signal and flow signal of thermal measurements?
DS : temperature T (*C)
FS : heat flow q (watts)
What is the difference signal and flow signal of concentration measurements?
DS : solute concentrations C (mg/mL)
FS : solute flow Q (mg / min)
What does DC stand for?
direct current
consistent straight line about non zero number
What does AC stand for?
alternating current (varies around zero)
What type of current does the cardiovascular system use?
DC + AC
varies around non zero number
Arterial blood pressure waveform is based on what 2 measurements?
Mean pressure and pulse pressure
When is mean circulating filling pressure measured?
When flow is stopped, therefore the heart is stopped, and thus value should be very close to 0
What is frequency?
Number of variations / sec
What is Coulomb’s law?
F = k (q1 x q2 / d^2) f = force , q = charge strengths d = distance between charges k = coulomb's constant
What does coulomb’s law measure?
relationships of charges
What is formula for frequency?
f = 1/T
When using the “right hand rule” in magnetic fields, what does thumb point to and what does fingers point to?
Thumb points to positive end.
Fingers point towards magnetic field
What is the equation of power?
P = I V power = current x voltage
What does Kirchhoff’s Voltage law state?
The sum of the voltage variations around a loop is zero
Rt = R1 + R2 + R3
What type of series system do humans have?
Closed system but not series system
What are the only things in human body that can vary resistance?
Arterioles
What is Kirchhoff’s Current Law?
Sum of all currents that converge on a node will be zero
When adding parallel resistances, is the total resistance reduced or increased?
Reduced
V = 0 when multiplied cross products are equal to each other ( R1 x R4 = R2 x R3). This is known as what?
The wheatstone bridge , or the balance equation
When is the wheatstone bridge used ?
Used in pressure transducers
What is a transducer?
device that converts one form of energy to another form
The ratio of the change in an electric charge in a system to the corresponding change in its electric potential is known as what?
Capacitance or compliance
T or F : Capacitors can hold charges and keep those charges separated.
TRUE
When parallel capacitors are placed in a circuit, are they additive or subtractive?
Additive
Ct = C1 + C2 + C3
Parallel capacitance is dependent on what?
The area of the plates and the distance between the plates.
What is the equation of Capacitance?
C = kEo x (A/d)
Decreasing the distance between the plates will do what do capacitance?
They will become much more compliant
What major organ in the human body relies heavily on parallel capacitance?
Lungs
What type of capacitance is not found in the human body?
Series capacitance
Inductors, or inertance, is what?
Measure of the pressure gradient in a fluid required to cause a change in flow-rate with time
What is the major driving flow in hemodynamics?
Blood
What do inducers do?
They try to resist current change in the circuit
What type of inductance systems are most circulatory systems?
Parallel inductance systems
T or F: Various parts of the human body have different types of resistance?
TRUE
What is the capacitive reactance equation?
Xc = 1 /
2 (pi) f C
If you have poorly compliant lungs, what kind of ventilation to you need to give to the patient?
High frequency ventilation because the higher the f, the less the reactance
What is the phase(time) difference that results from the human physiological system?
90 difference
What is impedance?
The sum of resistance, capacitive reactance, and inductive reactance taking the phase contribution of each into account
What is the formula for impedance?
Z = square root (R^2 + (Xl - Xc)^2)
Why is the baseline heart rate between 60-70 bpm?
Because the compliance and inertia of the heart cancels each other out, therefore it is the moment at which it is most efficient
What sizes do the bandwidth filters come that are used in accordance with the AHA?
What are these filters called?
0.5- 100 hz
Band pass filter
A main source of EKG interference is what?
60 cycle EKG
What does a band reject(notch) filter do?
Cuts out many bands of frequencies
What is the peak amplitude?
The maximum amplitude in either the positive or negative half cycle
What is the RMS amplitude (root mean square)?
The amplitude a DC signal would need to be in order to provide the same average power peak amplitude
