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Physics > Module 6 > Flashcards

Module 6 Flashcards

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1
Q

What is a capacitor

A

2 metallic plates seperated by an insulator

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2
Q

Define dielectric

A

Insulator seperating 2 plates in a capacitor

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3
Q

How does a capacitor store charge

A

When the capacitor is connected to the cell, electrons flow from the cell.
The breif current means electrons are removed from plate A of the capacitor and deposited onto the other plate B. Plate A becomes positively charged (loss of electrons) and plate B becomes negatively charge.

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4
Q

What happens when a capacitor is charged

A

The plates have equal and opposite charge (Q) so there is a p.d. across the plates

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5
Q

When is the equation X=Xo (1-e^-t/RC) used

A

when X can be either V or Q

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6
Q

What type of current is the domestic supply

A

Alternating

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7
Q

What is smoothing capacitors

A

A diode is used to make an alternating current flow only in one direction
With a capacitor the output voltage is smoothed out

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8
Q

What is a feild

A

A region in which an object experiences a force

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9
Q

State coulombs law

A

Any 2 point charges exert an electrostatic force on each other that is directly proportional to the product of their charges and inversly proportional to the square of the distance between them

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10
Q

Similarities between electric feilds and gravitational feilds

A

Both are radial feilds
Both follow inverse square law

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11
Q

Differences between electric feilds and gravitational feilds

A

Gravitational feild is always attractive

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12
Q

For a charged particle in an electric feild how is the horizontal motion affected

A

No acceleration (constant v)

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13
Q

For a charged particle in an electric feild how is the vertical motion affected

A

Acceleration = F/m or EQ/m
Suvat can be used

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14
Q

How to find work done from force distance graph

A

Area underneath

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15
Q

Define electric potenitial

A

Electric potential at a point is equal to the work done per unit charge in bringing a positive charge from infinity to that point

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16
Q

Define electric potential difference

A

Work done per unit charge between two points around the particle of charge Q

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17
Q

What is an equipotential line

A

A line along which electric potential is the same

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18
Q

Where do magnetic feild lines act around the earth

A

From South of the earth to north
(north magnetic pole to south magnetic pole)

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19
Q

What rule determines the direction of a magnetic feild

A

Right hand grip rule

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20
Q

Define magnetic flux density

A

The strength of the feild

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21
Q

How does a velocity selector work

A

2 parallel horizontal plates connected to a power supply produces a uniform electric feild between the plates (strength E)
A unifrom magnetic feild (strength B) is applied perpendicular to the electric feild.
The charged particles travelling at different speeds can be sorted through a narrow slit.
Since electric and magentic fields deflect them in opposite directions, only particles witha a specific speed will the directions cancel out.
Only particles with this specific speed will pass through the second slit.

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22
Q

How does a mass spectrometer work

A

Only particles with the same velocity enter a unifrom magnetic feild
Each ion is deflected a different amount by the detector to fin mass

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23
Q

What is a hall probe

A

Used to measure magnetic flux density

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24
Q

Define magnetic flux

A

The product of the component of the magnetic flux density perpendicular to the cross sectional area.

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25
Q

Define magnetic flux linkage

A

The product of the number of truns in the coil and the magnetic flux

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26
Q

SI unit of flux linkage

A

Weber

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27
Q

State Faradays law

A

The magnitude of the incident emf is directly proportional to the rate of change of magnetic flux linkage

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28
Q

State Lenz law

A

The magnitude of the incident emf is inversely proportional to the rate of change of magnetic flux linkage

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29
Q

What is a step up transformer

A

Has mor turns on the secondarly coil than the first

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30
Q

What is a step down transformer

A

Has fewer turns on the secondary coil than the primary

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31
Q

Conclusion of ruthorfords alpha scattering experiment

A

Most of the alpha particles passed straight through so most of the atom is empty space with most of the mass concentrated in the nucleus
Alpha particles near th nucleas were repelled so the nucleus must be positively charged

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32
Q

What is an isotope

A

Nuclei of the same element that have a different number of neutrons

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33
Q

What is the nucleon number

A

Total number of protons and neutrons

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34
Q

What is the atomic number

A

Number of protons present

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35
Q

What is the atomic mass unit

A

1.66x10^-27 or 1 twelfth of the mass of a carbon 12 atom

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36
Q

What is the nuckear strong force

A

Attractive gravitational force between the protons (overcoming magnetic repulsion)

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37
Q

Under what range is the strong force attractive

A

0.5-3fm

38
Q

What is the weak nuclear force

A

Responsible for beta decay

39
Q

What are hadrons

A

Particles and antiparticles affected by strong nuclear force and weak nuclear force
Made up of quarks
(protons, neutrons and mesons)

40
Q

Leptons

A

Particles and antiparticles unaffected by strong nuclear force
(electrons, neutrinos, muons)

41
Q

What are the fundemental particles

A

Quarks and leptons

42
Q

Types of quarks

A

up down strange charm top bottom

43
Q

What are baryons

A

Hadroms made of 3 quarks

44
Q

What are mesons

A

Hadrons made from quark antiquark pair

45
Q

Beta minus decay

A

Neutron = proton + electron + electron antineutrino

46
Q

Beta plus decay

A

proton = neutron + positron + electron neutrino

47
Q

Explain alpha radiation

A

2 protons and 2 neutrons
highly ionising
not penetrating (stopped by a sheet of paper)
positively charged

48
Q

Explain beta radiation

A

Fast moving electrons or positrons
stopped by 1-10mm of aluminium
positively and negatively charged depending on type

49
Q

Explan gamma radiation

A

High energy photons
not very ionising
highly penetrating (stopped by 1-10cm of lead)
uncharged so unaffected by magnetic feilds

50
Q

Define random

A

Cannot predict when next decay will be
each nucleus has equal chances of decaying per unit time

51
Q

Define spontanious

A

Unaffected by presence of other nuclei in the sample
Unaffected by external factors such as pressure

52
Q

Define half life

A

Time taken for number of active nuclei in a sample to half

53
Q

Define activity

A

Rate at which nuclei decay

54
Q

Define decay constant

A

Probibility of decay of an individual nucleus per unit time (A/N) (lambda in the booklet)

55
Q

How does carbon dating work

A

Measuring ratio of carbon 14 to carbon 12 of dead material and similar living material.

56
Q

What is annihilation

A

When a particle and antiparticle meet and their mass is turned into energy

57
Q

Define mass defect

A

Difference between the mass of the completely seperated nucleaons and the mass of the nucleus

58
Q

Define binding energy

A

Minimum energy required to completely separate a nucleus into its seperate protons and neutrons

59
Q

what does high binding energy per nucleon

A

The more tightly bound the nucleons within the nucleus are

60
Q

Define nuclear fission

A

An unstable uranium 235 nuclei splits into 2 halves after absorbing a nutron
Also releases more neutrons

61
Q

What is a moderator used for in a fission reactor

A

Slow down fast paced neutrons

62
Q

What is a control rod used for in a fission reactor

A

Material to absorb neutrons

63
Q

What is nuclear fusion

A

Bring nuclei within 10^-15 fm so strong nuclear force becomes attractive
Has to be at high enough temperatures

64
Q

What is thermionic emmision

A

emission of electrons througb heating at the cathode

65
Q

What is the anode in an X ray

A

Target metal such as tungsten (high melting point)
Undergoes attenuation mechanisms

66
Q

Define simple scatter

A

Range of 1-20keV
X ray photon bounces off

67
Q

Define photoelectric effect in X rays

A

less than 100keV
X ray photon is absorbed and electron is released

68
Q

Define compton scattering

A

0.5-5MeV
Electron is released and X ray released with reduced energy

69
Q

Define pair production

A

> 1.02MeV
X ray dissapears and creates electron and positron

70
Q

Define contrast medium

A

Elements with large atomic numbers so higher attenuation coefficient
Barium for digestive system
Iodine for blood flow

71
Q

What is a CAT scan

A

Fan shaped beam of X rays absorbed at the other side by detectors
X rays attenuated by different amounts by different tissues
Fan complets 360 degrees and table is moved through the ring a bit more

72
Q

Downsides of CAT scans

A

Ionising
expensive
time consuming

73
Q

Positives of CAT scans

A

3D image
can distinguish between different tissues

74
Q

What is a radioisotope

A

Gamma source w short half life placed inside the patient
Eg florine 18

75
Q

What is a radiopharmecutical

A

Medical tracer which is a radioisotope made to reach the correct place
Concentrations can identify irregularities in the body

76
Q

Define colimator

A

Honeycomb of long thin tubes
Any photons arriving at an angle are absorbed

77
Q

Define scintillator

A

Produces viable light from incoming x ray photons

78
Q

Define photomultiplier

A

Viable light from scintillator is multiplied into a voltage to be connected to a computer and modelled

79
Q

What is a PET scan

A

Gamma radiation used to make 3d image
Use a medical tracer that our body thinks is glucose (flourodeoxyglucose)

80
Q

Advantages of PET scan

A

3d image
non invasive

81
Q

Disadvantages of PET scan

A

Expensive tracers and equipment

82
Q

Ultrasound benefits

A

non ionising
non invasive

83
Q

What is the peizoelectric effect

A

peizocrystel compressed and streched produces an alternating current and vice versa
The frequency of oscillation is the natural frequency of the crystal

84
Q

Define transducer

A

used to detect ultrasound

85
Q

What is an A scan

A

Simple ultrasound
Each pulse of ultrasound is partially reflected by different tissues which is recieved at the transducer and displayed on an oscilloscope
speed and time used to measure distance

86
Q

What is a B scan

A

2D image
each position of transduce produces a row of dots which corresponds to a boundry
brightness of the dot is proportional to intensity of reflected ultrasound
computer can turn this into an image

87
Q

What is coupling gel

A

gel with similar acoustic impedance to skin which stops relfections at skin boundry
(impedance matching)

88
Q

What is a doppler ultrasound used for

A

track blood clots, movement of blood and speed

89
Q

How does intensity effect realeased photon energy

A

It doesnt photon energy is inependent of intenisty

90
Q

voltage in x rays

A

High voltage

91
Q

Electrons thru graphite show what

A

electrons travel in waves

92
Q

Current used in transformers

A

alternating

Physics (26 decks)

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