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Summary A Level Physics Definitions

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Course
Breadth In Physics

Institution
OCR

Book
A Level Physics A for OCR Student Book

This covers all the definitions and small notes (300+) collected from past exam papers across years. Topics Include: *MECHANICS *CAPACITANCE *MAGNETISM *COSMOLOGY *NEWTONIAN WORLD *SIMPLE HARMONIC MOTION *THERMAL PHYSICS *WAVES *QUANTUM PHYSICS *MEDICAL PHYSICS *Mainly intended for O...

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Summarized whole book? Yes
Uploaded on September 9, 2021
Number of pages 32
Written in 2019/2020
Type Summary

a level physics
ocr
sixth form
definitions
notes

Book Title:A Level Physics A for OCR Student Book

Author(s):Graham Bone, Nigel Saunders

Edition:juli 2015
ISBN:9780198352181
Edition:1

Study Level
A/AS Level
Examinator
OCR
Subject
Physics A
Unit
Breadth In Physics

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Define Electric Field Strength Electric field strength at a point in space is the force per
unit (positive) charge
Define Magnetic Flux Density a measure of the strength of a magnetic field at a given
point, expressed by the force per unit length on a
conductor carrying unit current at that point.
F=BQv
Define Tesla One Tesla is the uniform magnetic flux density which,
acting normally to a long straight wire carrying a current of
1 ampere, causes a force per unit length of 1 on the
conductor
Define Magnetic flux magnetic flux = magnetic flux density x (cross-sectional)
area (perpendicular to field direction)
B x A (normal to B). Magnetic flux=magnetic field x Area
Define The Weber One Weber is equal to one Tesla metre²
Define Magnetic Flux Linkage The change of magnetic flux linkage is equal to the
product of the change in magnetic flux and the number of
turns N of a conductor involved in the change in flux
Define Capacitance Capacitance = charge per (unit) potential differences
Ratio of charge to potential for a conductor
Define The Farad coulomb per (unit) volt
Define The Time Constant of a Time for the charge to have decreased to of its initial
Circuit
charge

Define Proton Number The number of protons found in the nucleus of an atom
Define Nucleon Number The mass number, the sum of the number of neutrons
and protons in an atomic nucleus
Define Isotopes Isotopes are different forms of the same element which
have the same number of protons but different numbers
of neutrons in their nuclei
Define Activity (Radioactivity) Spontaneous emission of a stream of particles or
electromagnetic rays in nuclear decay
Define The Decay Constant The probability of decay of a nucleus per unit time
Reciprocal of decay time
Define Half Life The half-life of a radioactive nuclide is the time taken for
the number of un-decayed nuclei to be reduced to half its
original number
Define Binding Energy The energy equivalent of the mass defect of a nucleus. It
is the energy required to separate to infinity all the
nucleons of a nucleus
Define Binding Energy Per Binding energy per nucleon is defined as the total
Nucleon (minimum) energy needed to completely separate all the
nucleons / protons and neutrons in a nucleus divided by
the number of nucleons in the nucleus
Define Intensity Power per unit area(W/m²)
Define The Distance Measured The astronomical unit is defined as the radius of the
In Astronomical Units (AU) circular path round the sun followed by a body in 365.25
days
Define The Distance Measured Distance from a base length of 1 AU that subtends an
In Parsecs (pc) angle of 1 (arc) second
Define The Distance Measured The distance travelled by electromagnetic radiation (light)
In Light-Years (ly) in one year
Define Critical Density The density above which it is believed the expansion of
the universe will slow down and reverse

,State that electric fields are Electric charges exert forces on each other when they are
created by electric charges a distant apart. An electric field is a region of space where
a stationary charge experiences a force
State and use Fleming’s left- If the first two fingers and thumb of the left hands are
hand rule to determine the force placed at right angles then the first finger is in the
on a current conductor places at direction of the field, the second in the direction of the
right angles to a magnetic field. current and the thumb in the direction of motion
State and use Faradays Law of Induced e.m.f is proportional to the rate of change of
electromagnetic induction (magnetic) flux
State and use Lenz’s law The direction of the induced e.m.f is such as to cause
effects to oppose the change producing it
State and use the equation for
the total capacitance of two or
more capacitors in parallel
State and use the equation for for two capacitors in series you can
the total capacitance of two or
more capacitors in series use the equation
State and use the notation
for the representation of
nuclides
State the quantities conserved The charge, the total number of neutrons and protons,
in a nuclear decay total energy, the total momentum of the system and the
total lepton number.
State that there are two types of β decay
State that (electron) neutrinos decay plus antineutrino
and (electron) antineutrinos are decay plus neutrino
produced during and
decays respectively
State that a particle is an electron and a particle is a positron
State that electrons and neutrinos are members of a group of particles known as leptons
State the approximate
magnitudes in meters of the
parsec
State the approximate value in
meters of the light-year
State Olbers’ paradox Based on: the universe being static / homogeneous and
infinite / infinite number of stars
State and interpret Hubble’s law The speed of recession of a galaxy is proportional to its
distance (from Earth / observer)
State the cosmological principle Universe is isotropic /same in all directions
Homogeneous / evenly distributed
Explain the effect of a uniform If E is uniform, then the acceleration of the charged
electric field on the motion of a particle is constant. If the particle has a positive charge,
charged particle then its acceleration is in the direction of the electric field.
If the particle has negative charge, then its acceleration is
in the direction opposite the electric field
Explain the use of deflection of Depending on the strength of the magnetic and electric
charged particles in the fields the mass of charged [articles detected can be
magnetic and electric fields of a changed. E.g: the smaller the electric field the larger
mass spectrometer massed particles can be detected
Explain that the area under a potential difference against charge graph is equal to the
energy stored by a capacitor
Explain exponential decays as having a constant ratio property

,Explain that since protons and neutrons contain charged constituents called quarks they are
therefore not fundamental particles
Explain how soft tissues like the In order to make soft tissue more visible, contrast media,
intestines can be images using such as barium, are used. The patient swallows a liquid
barium meal rich in barium as it will readily absorb X-rays. The barium
meal coats the wall of the tract enabling its outline to be
seen in X-rays.
Explain what is meant by the Doppler effect is a change in frequency and wavelength
Doppler effect of a wave. It is caused by the change in distance between
the thing creating the wave and whatever is measuring,
seeing or hearing the wave.
Explain qualitatively how the Doppler effect uses ultrasound waves. Sound waves are
Doppler effect can be used to reflected by the moving blood cells. Change in
determine the speed of blood frequency/wavelength enables the speed of blood flow or
rate of flow of blood to be found
Explain how ultrasound Transducer is the name given to any device that converts
transducers emit and receive energy from one form to another. In this case electrical
high frequency sound energy is converted into ultrasound energy by means of a
piezo-electric crystal such as a quartz
Explain that the standard model galaxies are moving apart / universe is expanding
of the universe implies a finite if galaxies have always been moving apart then at some
age for the universe (hot big stage they must have been closer together / or started
bang) from a point
evidence in red shift either optical / microwave
further away the galaxy the faster the speed of recession
the existence of a (2.7 K) microwave
background radiation
there is more helium in the universe than expected
Explain that the universe can be Open: Universe expands for all time
‘open’, ‘flat’ or ‘closed’, Flat: expands to a limit (but never reaches it)
depending on its density
Closed: Universe contracts / collapses back
Explain that the ultimate fate of if average density of the Universe is less than critical then
the universe depends on its it will be too small to stop it expanding / it goes on forever
density if the average density of the Universe is greater than the
critical value it will cause the contraction (and produce a
big crunch)
close to critical value and therefore a universe expands
that will go towards a limit / expands at an ever
decreasing rate asymptotic
Explain that it is currently Estimates give values of 1 or 2 orders of
believed that the density of the
universe is close to, and magnitude less than critical. But rotation of galaxies show
possibly exactly equal to, the they have more mass than we can see, and the
critical density needed for a ‘flat’ inflationary expansion theory suggests that the density is
cosmology exactly equal to critical
Describe the difference A-scan in one direction only / range or distance or depth
between A-scan and B-scan finding
B-scan uses a number of sensors or a sensor in different
positions / angles (to build up a 2D/3D image)
Describe the importance of The greater the mismatch, the more ultrasound is
impedance matching reflected
Describe the principle contents There are at least galaxies in the universe. From a
of the universe, including stars, side view there is a disc shaped conglomeration of stars
galaxies and radiation with a bulging central nucleus

, Describe the solar system in Solar system contains 9 well known planets and their
terms of the Sun, planets, satellites; it also contains a number of small or dwarf
planetary satellites and comets planets. These planets all orbit the sun. Comets have an
elliptical orbit, which means that they return regularly
often passing close enough to the earth to be visible
Describe the formation of a star, Gas / dust (cloud) / nebula / (hydrogen) gas drawn
such as our Sun, from together by gravitational forces
interstellar dust and gas. Gravitational collapse
Temperature of (dust) cloud increases / KE (of cloud)
increases / (cloud) heats up (Loss in (gravitational) PE /
KE increases / PE changes KE / temperature increase)
Fusion occurs (when temperature is about 107K
Protons / hydrogen nuclei combine to make helium
(nuclei) (Fusion of protons / hydrogen nuclei
(produces helium nuclei and energy))
Stable sized star is produced when thermal / radiation
pressure is equal to gravitational pressure
Describe the Sun’s probable When hydrogen runs out the outer layers of the star
evolution into a red giant and expands / core shrinks
white dwarf Red giant formed / eventually (the core becomes) a white
dwarf
[A white dwarf is:
A very dense star
Hot star / high surface temperature / low luminosity
No fusion reactions take place / leaks away photons (from
earlier fusion reactions)
Its collapse is prevented by Fermi pressure / mass less
than 1.4 solar masses]
Describe how a star much more (When hydrogen / helium runs out) the outer layers of the
massive than our Sun will start expands / a (super) red giant is formed
evolve into a super red giant The core (of the star) collapses (rapidly) / a supernova is
and then either a neutron star or formed
black hole. (Depending on the initial mass of the star, a supernova is)
followed by neutron star / black hole

Describe and interpret Hubble’s Observations that the wavelengths of identifiable spectral
red shift observations lines in the spectra of light from distant galaxies did not
correspond with wavelength measured on earth. Column
of light seemed to be shifted towards the red end of the
spectrum. This was interpreted as a continuous
expansion of the universe
Describe and explain the Leftover radiation (stretched over time) from events in the
significance of the 3K Big Bang.
microwave background
radiation
Describe qualitatively the (At the start it was) very hot / extremely dense / singularity
evolution of universe All forces were unified
after the big bang to the present Expansion led to cooling
Quarks / leptons soup
More matter than antimatter
Quarks combine to form hadrons / protons / neutrons
Imbalance of neutrons and protons / (primordial) helium
produced.
Atoms formed

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