Combo Flashcards
(101 cards)
Astronomical unit (AU)
The average distance between the Earth and the Sun.
Parsec (pc)
The distance that gives a parallax angle of 1 arc second
Light year (ly)
The distance light travels in a vacuum in 1 year
Olber’s paradox
For an infinite, uniform and static universe the night sky should be bright not dark because of light received in all directions from stars
Hubble’s Law
The recession speed of distant galaxies is directly proportional to their distance from the observer
Cosmological principle
The universe is homogenous, isotropic and the laws of Physics are the same at all points within it
Critical density
The density of the universe which would cause it to be flat – i.e. the expansion rate would tend towards zero in infinite time.
(Stellar) parallax
The apparent shifting in position of a star relative to the background of distant stars when observed from different positions in the Earth’s orbit round the Sun.
Capacitance
The stored charge in a capacitor per unit potential difference across the plates.
Farad
The capacitance of a capacitor which stored a charge of 1C when a voltage of 1V is across the plates.
Capacitors in series
Same as resistors in parallel
Capacitors in parallel
Same as resistors in series
Capacitors in parallel
Same as resistors in series
Capacitive time constant
The time taken for the current, charge and p.d. for a capacitor to fall to 1/e (37%) of its original value when discharging through a resistor.τ = RC
Proton number (or atomic number)
The number of protons in the nucleus of an atom
Neutron number
The number of neutrons in the nucleus of an atom
Nucleon number (or mass number)
The number of protons and neutrons in the nucleus of an atom
Plum Pudding model
A model of the atom in which negative charges are distributed throughout a sphere of positive charge
Isotope
An atom with the same number of protons in the nucleus but a different number of neutrons
Conservation of ___
The total ___ before a nuclear change will equal the total ___ after.
Quantities conserved in nuclear decay
Nucleon number, mass-energy, lepton number, baryon number, charge
Atomic mass unit
A 1/12th the mass of a C-12 nucleus
Thermal neutron
These are slow-moving neutrons
Control rods
Rods of a neutron-absorbing material used to reduce the rate of a nuclear chain reaction