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Physics > Lecture 9 Formulas > Flashcards

Lecture 9 Formulas Flashcards

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1
Q

Conventional vs Electron Current

A

Conventional current goes opposite of electron flow

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2
Q

Circuit Definition

A

A collection of elements and signals, connected together for purposes of modifying input signals to obtain other desired signals or responses.

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3
Q

Ohm’s Law and Corollary

A

V=IR
Voltage = current x resistance
P=QR
Pressure = flow x resistance

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4
Q

Flow and Difference Analogies

A

Voltage is like pressure is like Temperature is like concentration
Current is like flow is like heat flow is like solute flow

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5
Q

Frequency (f) and period (T)

A

f=1/T
Heart rate of 120 bpm
T= 1minute/120beats x 60sec/1min = 0.5 s/beat
Frequency = 1/T = 1/0.5 = 2Hertz

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6
Q

Right hand rule

A

Using your right hand curled, your thumb points in the direction of the current and your curled fingers show the direction of the magnetic field.

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7
Q

Coulomb’s Law

A 
F=k (q1xq2)/d^2
f = force
q = charge strength
d = distance between charges
k = coulomb's constant
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8
Q

Power

A

P=IV

Power = Current x Voltage (electric potential)

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9
Q

Series Resistance

A

Kirchhoff’s Voltage Law: The sum of the voltage variations around a loop is zero
Rt=R1+R2+R3…

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9
Q

Principle of an attenuator

A

If you have have 5 equal resistors in series and you measure the potential across one resistor you observe 20% of the total potential.
If you measure the potential across 4 resistors you observe 80% of the total potential

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9
Q

Parallel Resistors (vascular analog)

A

Kirchhoff’s Current Law: The sum of all currents that converge on a node will be zero
1/Rt=1/R1+1/R2+1/R3+…

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9
Q

Parallel Capacitance

A

Ct=C1+C2+C3+…
Think of it as bringing the parallel circuits together and making one giant capacitor.
Venous system can hold 20 times the volume of the arterial system. Fun fact

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10
Q

Series Capacitance

A

1/Ct=1/C1+1/C2+1/C3+…
Bring the capacitors together and eventually the charges on either side cancel each other out to make only 1 effective capacitor.

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11
Q

Capacitors

A

Capacitance (compliance)
The ratio of the change in an electric charge in a system to the corresponding change in its electric potential
C=q/V

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12
Q

Splanchnic Circulation

A

Most circulatory systems are parallel systems.

Shows an example of how there is parallel resistance, series resistance, series inductance, and parallel capacitance.

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13
Q

Series Inductance

A

Lt=L1+L2+L3+…
Inductors are basically large coils of wire. In series is as though you’re adding the coils of wire to make one big coil.

14
Q

Inductive Reactance

A

XL=2pi x f x L

Inductive reactance directly proportional to frequency.

16
Q

Capacitive Reactance

A

XC=1/(2pi x f x C)

Capacitive reactance inverselyproportional to frequency.

17
Q

Capacitive vs Inductive Reactance

A

Are inversely related. There is a 90 degree phase difference. Potential capacitance is at it’s peak when potential inductance is at zero and vice versa.

18
Q

Impedance

A

Z=(R^2 + (XL-Xc)^2)^1/2

18
Q

Band-regect

A

Takes output from across a resistor to select a range of frequency that is rejected.

19
Q

Band pass

A

Takes output from across an inductor and capacitor combination to select a frequency range that is accepted

20
Q

EKG readings

A

Normal band pass is 0.05-100Hz

  1. 15-30 Hz slightly worse with St-depression
  2. 5-30 Hz doesn’t show ST elevation
  3. 0-30 Hz shows reduced baseline when observing ST elevation.
24
Q

Transformers

A 
Vsec/Vpri - Nsec/Npri
sec= secondary winding
pri= primary winding
Transformers are two coils of wire next to each other with individual circuits.
N= number of turns
25
Q

Root Mean Square

A

The amplitude a DC signal would need to be in order to provide the same average power = (0.707) peak amplitude.
You actually square, then mean, then root

26
Q

Electric Current

A

Flow of charge per unit time

27
Q

Electric Voltage

A

Potential energy required to move a charge of one coulomb from point A to point B

28
Q

Time constant (circuits)

A

Time constant is capacitance x resistance

Time constant is Inductance (L) divided by Resistance

29
Q

Wheatstone Bridge

A

The Balance Equation commonly used in transducers.
V=0 when R1 x R4 = R2 x R3 (equal cross products)
Usually 3 of the four are fixed resistance and the fourth is calibrated

Physics (12 decks)

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