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Physics G485
| Term | Definition |
|---|---|
| Define Electric Field Strength, E | Electric field strength at a point in space is the force per unit (positive) charge. E=F/Q. E=V/d |
| Define Magnetic Flux Density, B | F=BILsinӨ, where F is the force on a wire of length L carrying a current I at an angle Ө to the field. F=BQv(sinӨ). F=BIL(sinӨ) |
| Define Tesla, T | One Tesla is the uniform magnetic flux density when a wire of length 1m and carrying a current of 1A at a right angle to the field experiences a force of 1N. |
| Define Magnetic flux, Φ | Φ = BAcosӨ where B is the magnetic flux density, A is the area the flux passes through at right angles, and Ө is the angle between the plane of the area and the projection surface. |
| Define The Weber, Wb | The magnetic flux when a magnetic field of flux density 1T passes at right angles through an area of 1m2 1Wb = 1Tm-2 |
| Define Magnetic Flux Linkage | The magnetic flux through the coil x the number of turns on the coil. Flux linkage = N Φ |
| Define Capacitance, C | Capacitance = charge stored per unit potential difference. Ratio of charge to potential for a conductor (C=Q/V) Energy stored by a capacitor(W) = 1/2QV = 1/2CV2 = Q2/2C |
| Define The Farad, F | One coulomb per volt. 1F = 1CV-1 |
| Define The Time Constant of a Circuit | Time for the charge to have decreased to of its initial charge. Time constant = CR |
| Define Proton Number, Z | The number of protons found in the nucleus of an atom |
| Define Nucleon Number, A | The mass number, the sum of the number of neutrons and protons in an atomic nucleus |
| Define Isotopes | Define Isotopes Different forms of the same element (two nuclides) 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, λ | The probability of decay of a nucleus per unit time Reciprocal of decay time. A = λN |
| Define Half Life (of a radioactive nuclide) | Time taken for the number of un-decayed nuclei to be reduced to half its original number |
| Define Binding Energy | The energy required to separate all the nucleons of a nucleus. The energy equivalent of the mass defect of a nucleus. |
| Define Binding Energy Per Nucleon | The total minimum energy needed to completely separate all the nucleons in a nucleus, divided by the number of nucleons in the nucleus |
| Define Intensity | Power per unit cross sectional area(W/m²) |
| Define The Distance Measured In Astronomical Units (AU) | The mean distance from the centre of the Earth to the centre of the Sun. |
| Define The Distance Measured In Parsecs (pc) | Distance from a base length of 1 AU that subtends an angle of 1 (arc) second |
| Define The Distance Measured In Light-Years (ly) | The distance travelled by light in one year |
| Define Critical Density | The density above which it is believed the expansion of the universe will slow down and reverse |
| State and use Faradays Law of electromagnetic induction | Induced e.m.f is proportional to the rate of change of (magnetic) flux |
| State and use Lenz’s law | Direction of any induced current is in a direction that opposes the flux change that causes it. Lenz + Faraday: E= - Δ Φ / t |
| State and use the equation for the total capacitance of two or more capacitors in parallel | C = C1 + C2 + C3... |
| State and use the equation for the total capacitance of two or more capacitors in series | 1/Ct = 1/C1 + 1/C2 + 1/C3... |
| State the quantities conserved in a nuclear decay | The charge, the total number of neutrons and protons, total energy, the total momentum of the system and the total lepton number. |
| Beta minus decay | Neutron -> proton + electron + anti-neutrino |
| Beta plus decay | Proton -> neutron + positron + neutrino |
| State that electrons and neutrinos are members of a group of particles known as..? | Leptons |
| State the approximate magnitudes in meters of the parsec | 3.1 x 10^16 metres. |
| State the approximate value in meters of the light-year | 10 x 10^15 metres. |
| State Olbers’ paradox | With an infinite number of stars in an infinite universe, it does not matter which direction you look in - you will always see a star along the line of sight. therefore, the night will be as bright as the day sky. |
| State and interpret Hubble’s law | The speed of recession of a galaxy is proportional to its distance from the Earth |
| State the cosmological principle | Universe is isotropic /same in all directions Homogeneous / evenly distributed |
| Explain that the area under a potential difference against charge graph is equal to the..? | energy stored by a capacitor. W=1/2QV = 1/2CV2 = Q2/2C |
| Explain exponential decays as having a | constant ratio property |
| Explain how soft tissues like the intestines can be images using barium meal | The patient swallows a liquid 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 | Doppler effect is a change in frequency and wavelength 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 can be used to determine the speed of blood | Doppler effect uses ultrasound waves. Sound waves are reflected by the moving blood cells. Change in frequency/wavelength enables the speed of blood flow or rate of flow of blood to be found |
| Explain how ultrasound transducers emit and receive high frequency sound | In this case electrical energy is converted into ultrasound energy by means of a piezo-electric crystal such as a quartz |
| Explain that the universe can be ‘open’, ‘flat’ or ‘closed’, depending on its density | Open: Universe expands for all time Flat: expands to a limit (but never reaches it) Closed: Universe contracts / collapses back |
| Describe the difference between A-scan and B-scan | A-scan in one direction only / range or distance or depth 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 impedance matching | The greater the mismatch, the more ultrasound is reflected |
| Describe the solar system in terms of the Sun, planets, planetary satellites and comets | Solar system contains 9 well known planets and their satellites; it also contains a number of small or dwarf planets. These planets all orbit the sun. Comets have an elliptical orbit. They return regularly often close enough to the earth to be visible. |
| Describe the formation of a star, such as our Sun, from interstellar dust and gas. | -Hydrogen protons drawn together by gravitational forces (Gravitational collapse) -GPE decrease, KE increase. -Causes temp increase till fusion of protons occurs. -stable when thermal pressure = gravitational pressure |
| Describe the sun's probable evolution into a red giant and white dwarf | -Hydrogen runs out, core shrinks. -Pressure builds, causes core to expand. -Red giant formed. Eventually becomes white dwarf, which is: ->Very dense, high surface temp, no fusion takes place. ->Collapse prevented by Fermi pressure /mass < 1.4 Solar ma |
| Describe how a star much more massive than our Sun will evolve into a super red giant and then either a neutron star or a black hole | -Hydrogen runs out, core shrinks, red giant. -Core of the star collapses, supernova formed -Depending on initial mass, supernova results in neutron star or black hole. |
| Describe and interpret Hubble's red shift observations | Wavelength of identifiable spectral lines did not correspond to wavelengths measured on earth -Column of light shifted to red end of spectrum. -Interpreted as continuous expansion of the universe. |
| Describe and explain the significance of the 3K microwave background radiation | Leftover radiation (strecthed over time) from events in the big bang. |
| Describe qualitatively the evolution of the universe 10-43s after the big bang until present | -Very hot, all forces were unified. -Expansion led to cooling -Quarks / lepton soup -More matter than anti-matter -Quarks combine to form hadrons. -4:1 protons -Gravitational force responsible for forming stars / galaxies -Temp becomes 2.7K |
Created by:
Danletch
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