Heat and Temp

Question 1

what principle is a thermocouple based on

Answer 1

seebeck effect

Question 2

what is temperature

Answer 2

measurement of the average kinetic energy of the substance being measured

Question 3

what physical properties can be used to measure temperature

Answer 3

1. volume expansion
2. conductivity/resistivity
3. emisivity - electromagnetic
4. index of refraction

Question 4

examples of index of refraction

Answer 4

LC’s (liquid crystals)

Question 5

examples of conductivity/resistiviy

Answer 5

thermistor

heated wire

thermocouple

Question 6

examples of emisitivity

Answer 6

IR (infra red) dectector

Question 7

examples of volume expansion

Answer 7

mercury/alcohol

bimetallic strip (thermostat)

Question 8

use of a rapid reading nasal temperature can alternatively be used for what?

Answer 8

respiratory rate (if placed in the nare canal)

Question 9

How is heat is lost from body in the OR

Answer 9

1. Radiation (most of loss)
2. Conduction

Question 10

What are types of radiation and how much loss is accounted for

Answer 10

radiation 40%

convection 30%

evaporation 20%

Respiration 10% (8% evap of water, 2% heating of air)

Conduction 1-3%

Question 11

What does anesthesia do to the body’s temperature set point?

Answer 11

decreases to 35.5 C

(NMB – body can’t shiver)

Question 12

what is the triple point of water

Answer 12

ice, water, and water vapor exist in equilibrium

Question 13

what is water vapor pressue at tripple point?

Answer 13

4.58 mmHg

Question 14

What is the formula for K temp.

Answer 14

K = 273.15 + C

Question 15

what is the formula for F temperature

Answer 15

F= 32 + (9/5)C

C = 5/9(F - 32)

Question 16

what is true of heat

Answer 16

1. a quanity of measure that causes increaes or decrease in body temperature when added or taken away (respectively) provided that the body does not change state
2. form of energy
3. always transfered from area of higher temp to lower temp regarless total energy in either area.

Question 17

what is specific heat

Answer 17

amount of energy in calories required to raise the temp of 1 gram of the substance by 1 C.

water is used as standard (1 cal/gm C)

Question 18

what is the formula for heat

Answer 18

Q = M(C)(change in T)

Q is heat

M is mass

C is specific

T is temperature

Question 19

what is the specific heat of ice? steam?

Answer 19

a. 0.5 cal/(gm C)
b. same as ice

Question 20

what is the heat of fusion of ice

Answer 20

80 cal/gm

Question 21

what is the heat of vaporization of H20 at 100 C

Answer 21

540 cal/gm

Question 22

what are the latent phases of H20 as it changes phases

Answer 22

melting (80 cal)

vaporizing (540 cal)

Question 23

How is heat transferred form one object to another?

Answer 23

1. conduction
2. convection
3. radiation

Question 24

What is conduction?

Answer 24

transffer through the atomic and molecular collisions

(principle method of transfer in solids)

Question 25

What is convection?

Answer 25

warm currents of gas (i.e. air) or liquid are established through the distance in density between the warmer fluids and cooler fluids?

NOTE: gase and liquids are fluids

warm rises

cold falls

Question 26

What is radiation?

Answer 26

thermal energy transferred by electromagnetic waves

Question 27

What is forced convection? Example of use?

Answer 27

heated fluid is less dense than cooler so it rises (therefore if in a system that circulates it, it creates a current– convection current)

Forced - a pump forces cooler water from the bottom to passed through an area of warmer temp.

example - cooling of engine block by radiator fluids

Question 28

what is a function of absolute temperature of an object?

Answer 28

rate at which an object radiates energy

best radiators of thermal energy are best absorbers

Question 29

what is the formula, derived from Stefan-Boltzmann law for a radiative process

Answer 29

E = eσ (T₁⁴ -T₂⁴)

E is energy radiated per unit area

(clinical - muscle contraction, basal metabolic activity)

Question 30

in black body radiation of energy, what is E (energy) relationship to temperature?

Answer 30

E is proportional to absolue T⁴

Question 31

what is the formula for latent heat loss from the body

Answer 31

Ma = milgrams air breathed in/out per hour

Wo = expired air water content

Wi = inspired are water content

Lamda = latent heat of vaporization of H20

Question 32

what is the weight of 1 mole of air at STP

Answer 32

1 mol of air = 28.9 gm

Question 33

what is the approx latent heat loss via respiration at STP

Answer 33

≈ 200 cal/min

NOTE: more energy lost by vaporization than by direct waming of air

Question 34

Thermoregulatory system basics

Answer 34

3 components

1. sensory receptors
2. central integrator (controller)
3. effector organ systems

sensory receptors supply information to central integrator which compares recieved information to a set point (standard reference). Any difference signals an output form the central integrator to the effector organ system to increase or decrease heat production/loss therefor regulating temperature.