A2 Physics 2 1,2,3 Flashcards
Electric field strength
force of attraction per unit charge
Fleming’s left hand rule
The rule used to predict the direction of the force experienced by a current carrying conductor placed in an external magnetic field, T-motion, FF- field, SF- current
Magnetic flux density
B, the strength of a magnetic field. Defined a F/IL where F is the forced on a conductor of length L in the field carrying a current I at right angles to the magnetic field.
Tesla
The strength of a magnetic field that will produce a force of 1n on a current of 1A in a wire of 1m at right angles to the magnetic field
Magnetic flux
The product of magnetic flux density normal to the circuit and the cross-sectional area of the circuit
Weber
The magnetic flux of a field of strength 1 Tesla through a circuit of area 1m^2
Magnetic flux linkage
The product magnetic flux and the number of turns on a coil
Faraday’s law of electromagnetic induction
The induced emf in a circuit loop equals the rate of change of magnetic flux linkage
Lenz’s Law
The induced emf is in a direction which opposes the change producing it
Capacitance
The ratio of charge stored to the p.d across the plates of a capacitor
Farad
The capacitance of a pair of plates that can store 1 coulomb of charge for every 1V of p.d
Time constant
the time taken for the current, charge, and p.d for a capacitor to fall to 1/e of its original value when discharging through a resistor
proton number
the number of protons in the nucleus of an atom
Nucleon number
The sum of the number of protons and the number of neutrons in the nucleus of an atom
Isotope
Atoms of the same element with the same number of protons but a different number of neutrons
quantities conserved in nuclear decay
Proton number, Nucleon number, Mass- energy
Activity
The rate of decay of a nuclei in a radioactive sample
Decay constant
The probability that any particular atom of an isotope will decay per unit time
Half-life
The mean time taken for half the number of active nuclei in a radioactive sample to decay
Binding energy
The minimum external energy required to separate all the protons and neutrons in a nucleus
Binding energy per nucleon
The minimum external energy per nucleon required to separate all the protons and neutrons in a nucleus
Intensity
Power per unit cross-sectional area
Parsec
The distance when the stellar parallax is 1 arc second
Astronomical unit
The average distance from the earth and the sun
Light year
The distance light travels in a year
Obler’s paradox
For an infinite, static and uniform universe the night sky should be bright in all directions because of light received from stars
Hubble’s Law
The recessional speed of distant galaxies is directly proportional to their distance from the obsever
Cosmological principle
The universe is homogeneous and 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, the rate of expansion would tend towards zero in infinite time
