30 terms

# Fields, Particles and Frontiers of Physics (OCR Physics A)

#### Terms in this set (...)

tesla
SI unit for magnetic flux density; equivalent to 1 newton per ampere per metre
weber
SI unit for magnetic flux
farad
coulomb per volt
parsec
distance that gives a parallax angle of 1 arcsecond
electric field strength
force per unit positive charge
magnetic flux
magnetic flux density x area (perpendicular to field direction)
magnetic flux linkage
magnetic flux x the number of turns
capacitance
charge per unit potential difference
time constant of a circuit
time taken for current/charge/voltage of a discharging capacitor to fall to 37% of its original value (equal to the product of capacitance and resistance
proton number
number of protons in the nucleus of an atom (a.k.a. atomic number)
nucleon number
number of neutrons and protons in the nucleus of an atom (a.k.a. mass number)
activity
the rate of decay of nuclei in a radioactive sample
decay constant
probability of a decay of a nucleus per unit time
half life
the mean time taken for half the number of active nuclei in a radioactive sample to decay
binding energy
minimum energy to separate protons and neutrons of a nucleus
intensity
power per unit cross-sectional area
Faraday's law of electromagnetic induction
induced e.m.f. is proportional to the rate of change of magnetic flux
Lenz's law
the induced current or e.m.f. is in a direction so as to produce effects which oppose the change producing it
isotope
a version of an element with a different number of neutrons (but the same number of protons and electrons)
Doppler effect
the change in the frequency and wavelength of a wave caused by the relative movement between source and detector
piezoelectric effect
application of a p.d. across a crystal causes a vibration
Compton effect
x-ray photon interacts with electron; the scattered photon has a longer wavelength and the electron is ejected
Olber's paradox
if Universe is static and infinite, the night sky should be uniformly bright because every line of sight would end on a star
Hubble's law
the speed of recession of a galaxy is proportional to its distance
cosmological principle
universe has the same large-scale structure when observed from any point (homogenous, isotropic and the laws of physics are universal
3K microwave background radiation
gamma radiation released during the Big Bang has stretched as the Universe expanded, causing it to become microwave with an energy equivalent to a temperature of 3K
critical density
the density for which the universe will expand towards a finite limit (resulting in a flat universe)
open universe
universe will expand forever
flat universe
universe will expand towards a finite limit
closed universe
universe will contract (to a big crunch)
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