28-34;Magnets/Thermocouples/Pressure Transducers/Evaluation of VA Characteristic of crystal diode

Question 1

simple magnets

Answer 1

have 2 poles N/S
if N of 2 magnets brought together = repels, N+S attract

arrows along field lines = direction of magnetic field, density of lines = relative strength of magnetic fields

field strongest at pole, directed outwards from N

EG magnetic compass, needle is small magnet = rotates to align N pole/direction of earth’s magnetic field = used to map

Question 2

diamagnetic

Answer 2

when substances of small -ive magnetic character lines up at right angles to non-uniform magnetic field = exhibits paramagnetism

Question 3

ferromagnetism

Answer 3

result of long-range ordering of atoms of solids into domains = small ordered region = the domains act like a tiny magnet

EG Iron, Nickel

Question 4

what happens when u heat up magnet

Answer 4

destroys magnetic ordering = won’t show ferromagnetic property

Question 5

electromagnet

Answer 5

electric current flowing though straight wire to generate magnetic field

if long current-carrying wire bent into loop = magnetic fields add together inside loop = stronger magnetic field = solenoid

X - large current required for useful magnetic field

Question 6

how are practical electromagnetics made

Answer 6

adding iron core to solenoid = small magnetic field causes domains of iron’s ferromagnetic core to line up = produces additional magnetic field

Question 7

interaction btw electricity and magnetism

Answer 7

electricity and magnetism are manifestations of the same basic force = electromagnetic force

Question 8

does magnetic field exert force on charge

Answer 8

magnetic field exerts no force on a charge at rest or charge moving parallel to magnetic field

if MF small = charge passes through = deflects charge from OG path

if MG large enough to trap charge = charge moves in circular path = MF provides centripetal force necessary to move charge in circle

Question 9

electric motor principle

Answer 9

current-carrying wire in MF experiences force perpendicular to wire

Question 10

electric motor

Answer 10

collection of wire loops arranged on rotor suspended in MF and spins freely

when electric current flows through loops, force produced perpendicular to each section or wire

MF up on 1 side of coil, down on other = produces torque to rotate motor = moving coil meter

Question 11

magnetic flux

Answer 11

measure of no. of magnetic field lines that cross a given area

Question 12

faraday’s law

Answer 12

describes induction by relating EMF induced in circuit to rate of change of magnetic flux through circuit

-ive sign = induced magnetic field opposes the change that created it

EG Ultrasound scan, NMR imaging, doppler pulse

Question 13

sensing elements for physiological measurements/transducers

Answer 13

no. of physiological measurements made using sensors that covert physiological data to small electrical signals.

electrical image can be easily transmitted to remote monitoring point, amplified and displayed to be measured

Question 14

thermocouples

Answer 14

temp sensor consisting of junction between 2 different metals

2 tiny wires spot-welded together at sensing junction, ref junction connected to measuring device to measure thermal electromotive force/thermo emf

temp-voltage transducer = V depends on metal wire and Temp

Question 15

electrical resistance thermometer

Answer 15

thermal agitation of atoms of metal increases w/ temp = resistance to electric current flow increases

temp sensors of platinum wire

most accurate, cannot be miniaturised

Question 16

thermistor

Answer 16

similar to electrical resistance thermometer, electric resistance changes w/ temp = as R increases T decreases

can be miniaturised, more sensitive, easily calibrated, doesn’t have extreme accuracy

Question 17

pressure transducer

Answer 17

produces electrical signal proportional to pressure exerted upon it

EG. microphones=form electrical image of P variation in air caused by sound

Question 18

oximeter

Answer 18

EG of sensing element using light to determine O2 content of blood

small sample of blood illuminated w/ red light, reflected light from blood enters photoelectric cell = amount of light reflected determine % of O2 saturation of Hb

Question 19

electrodes for pH/CO2/O2

Answer 19

pH electrode = small glass bulb selectively permeable to H+, inside bulb is silver electrode coated w/ AgCl and immersed in buffer sol of pH1 = when electrode placed in liquid of unknown pH = diffusion process = small V on electrode = determines pH

Question 20

amplifiers

Answer 20

produce distortion free replica of OG signal

require large amount of electrical power to display physiological data

Question 21

display devices

Answer 21

numerical values in physiological data taken from display device

EG. oscilloscope

Question 22

transistor

Answer 22

found in amplifiers which use = miniaturized solid-state integrated circuits w/ many transistors

Question 23

oscilloscope

Answer 23

cathode ray oscilloscope display for monitoring physiological data

visual display of V varies w/ time

cardiac monitor = repetition rate + detailed shape of ECG V pattern +several physiological variables (SP/DP) observed

Question 24

meters and chart recorders

Answer 24

moving coil meter = current-carrying wire experiences force when placed in magnetic field = exerts force both sides = torque = proportional to current through coil = indicating needle attached to coil, its position calibrated in terms of coil

adopted to measure V or R

large resistor in series w/ coil = Voltmeter = I flowing thru coil proportional to V across combination

Ohmeter= battery ok known V in series w/ coil

x slow response

Question 25

digital display

Answer 25

LED/LCD = small and dependable = electrical signal converted to digital form = used for other functions

Question 26

defibrillator

Answer 26

high V device, large capacitor for emergency resuscitation from heart stoppage or ventricular fibrillation

momentary large I flows through heart - stops fibrillation and normal heart rhythm resumes

Question 27

electrosurgery/cautery

Answer 27

electrosurgical instruments used for cutting/welding tissue together

high I density/V freq causes cutting/cauterizing action