Quickfire flashcards

Question 1

What is the Hagen-Poiseuille equation?

Answer 1

Q = volumetric flow rate
ΔP = pressure difference across the length of the pipe
r = radius of the pipe
η = dynamic viscosity of the fluid
L = length of the pipe

Question 2

What is the equation for Reynolds’ number?

Answer 2

Re = (ρvL) /η

Q = volumetric flow rate
η = dynamic viscosity of the fluid
L = length of the pipe
ρ (rho) = fluid density
v = flow velocity

Question 3

What is Henry’s Law?

Answer 3

Henry’s law - Increasing the partial pressure of gas above a liquid will increase the amount dissolved in the liquid

P = Hv * M

P is the partial pressure of a gas
Hv is Henry’s proportionality constant
M is the molar concentration of gas

Question 4

What is standard temperature and pressure?

Answer 4

Standard Temperature
Temperature: 0°C (273.15 K)

Standard Pressure
1 atm (101.325 kPa)

Question 5

What is Boyle’s Law?

Answer 5

At a given temperature, the pressure of a gas is inversely proportional to the volume it occupies

PV = k

Boyle is boiling - the temperature is constant

Question 6

What is Charles’ Law?

Answer 6

At a given pressure, the temperature of a gas is proportional to the volume it occupies

V/T = k

King Charles is constantly under pressure - pressure is constant

Question 7

What is Gay-Lussac’s Law?

Answer 7

At a given volume, the pressure of a gas is proportional to its temperature

P/T = k

Gay-Lussac is a voluminous name - volume is constant

Question 8

What is the Ideal Gas Law?

Answer 8

Combination of the Boyle’s, Charles’ and Gay-Lussac’s Laws

PV = nRT

R is the universal gas constant (8.31)

Question 9

What is Graham’s Law

Answer 9

Rate of diffusion is inversely proportional to molecule size

Question 10

What is Avogadro’s Law?

Answer 10

At a set temperature and pressure, 1 mol (6.023x10²³ molecules) of any gas will occupy the same volume (22.4L at STP)

Question 11

Define Coulomb

Answer 11

The amount of charge that passes a point, when one ampere of current flows for one second - equivalent to 6.24x10^18 electrons

Question 12

Define Current

Answer 12

Current is the flow of charge over time, and is measured in Amperes

One ampere is 6.24x10^18 electrons/second

A = C/second

Question 13

Define Voltage

Answer 13

One volt is also the electromotive force that performs one joule of work for each coulomb of charge passing a given point

V = J/C

Voltage is calculated by multiplying current (I) by resistance (R) - Ohm’s law

V = IR

Voltage also equals watts/amp

V = P/I

Question 14

Define Power

Answer 14

The rate of energy expenditure, in Joules/second

P = VI

Question 15

Define Resistance

Answer 15

Resistance (R)
The extent to which a material prevents or reduces the flow of charge or electrons
Materials with very high resistance are designated insulators, as opposed to conductors.

More resistance means that more heat is given off

R = V/I

Resistors in series have a total resistance of R1+R2
Resistors in parallel have a total resistance of
1/R1 + 1/R2 = 1/Rtotal

Question 16

Define Impedance

Answer 16

Impedance (Z)
Similar to resistance, but applies to AC only
The sum of capacitance, inductance, and resistance of an alternating current, but depends on current frequency

Isolating capacity in diathermy circuits offers high impedance to gangerous mains frequency

Z = V/I

Question 17

Define Reactance

Answer 17

Reactance (X)
When the main load in a circuit is generated by an inductor or a capacitor, the term reactance is used rather than resistance

X = V/I

Question 18

Define Inductance

Answer 18

A conductor that generates an electromotive force when there is a change in current passing through it. It will also induce this force in any other conductors in close proximity.

Measured in Henry, with the symbol L

An inductor is a necessary part of a defibrillator, as the current and charge tend to decay rapidly, so the inductor prolongs the duration of current flow through the myocardium.

Question 19

Define Capacitance

Answer 19

Capacitance is the ability of a material to store electrical charge, measured in Farads (F)

One Farad indicates one coulomb of charge for every volt of potential difference

In AC, the direction of electron flow is constantly changing, resulting in the charge not building up. The use of capacitors with AC is only possible at much lower AC frequencies than are conventially seen

Question 20

Explain the levels of macroshock

Answer 20

Macroshock
Sensations felt for a given cutaneous shock:

Current | Effect
1mA Tingling sensation
5mA Painful shock
15mA Severe pain and contraction
30mA Unable to let go of wire
50mA Respiratory arrest
75-100mA VF
1000mA Severe burns

Question 21

What is Microshock

Answer 21

Microshock
Only 0.05-1mA required to induce VF when applied directly to the heart, due to bypassing resistance of skin and soft tissues - the causes of a microshock require a direct communication from the outside to the myocardium

Guidewires, pacing lines, and central lines flushed with a conducting fluid

Question 22

What are the classes of electrical equipment

Answer 22

Prevention of shock (Class)
Class I
Mains powered, earthed metal casing
Usually fused.
May only be connected to a patient if there is a non-earthed transformer that isolates the patient from the mains
Effective if there is a single failure between the live wire and case, but not if the earth is also damaged, as the case can become live, meaning that the patient can form part of the circuit to ground

Class II
Double insulated, no earth

Class III
Low voltage - less than 24V AC, usually battery powered