Definitions Flashcards
Absolute Zero
The lowest possible temperature at which substances have the minimum internal energy
Acoustic Impedence
The product of the density of a substance and the speed of ultrasound in that substance
Aphelion
The furthest point from the sun in an orbit
Archimedes’ Principle
The upthrust of an object is equal to the weight of fluid displaced
Attenuation
The decrease in the intensity of electromagnetic radiation as it passes through matter or space
Brownian motion
The continuous random motion of small particles suspended in a fluid, visible under a microscope
Chandrasekhar limit
The mass of a stars core beneath which the electron degeneracy pressure is sufficient to prevent gravitational collapse.
1.44 Solar masses
Coherance
Two waves sources, or waves, that are coherent have a constant phase difference
Cosmological principle
The assumption that the universe, when viewed on a large scale, is homogeneous and isotropic and the laws of physics applies everywhere
Coupling gel
A gel with the acoustic impedance similar to that of skin, that is smeared onto the transducer and the patients skin before and ultrasound scan in order to fill air gaps and ensure that almost all the ultrasound enters the patients body
Decay constant
The probability of a decay of an individual nucleus per unit of time
Faradays law
The magnitude of the induced EMF is directly praportional to the rate of change of flux linkage
Fundamental frequency
The lowest possible frequency at which an object can vibrate
Ideal gas
A model of a gas including assumptions similar to the behaviour of a real gas
Inelastic collision
A collision in which kinetic energy is transferred into other forms and is NOT conserved
Interference pattern
A pattern of constructive and destructive interference formed as waves overlap
Keplar’s First law of planetary motion
The orbit of a planet is an ellipse with the sun as one of the foci
Keplar’s Second law of planetary motion
A line segment connecting the planet and the sun sweeps out equal areas during equal intervals of time
Keplar’s Third law of planetary motion
The square of the orbital period is directly proportional to the cube of is average distance from the sun
Kirchoff’s First law
At any point in an electrical circuit, the sum of currents into that point is equal to the sum of the currents out of that point.
Electrical charge is conserved
Kirchoff’s Second law
In a closed loop of an electrical circuit, the sum of the EMF’s is equal to the sum of the PD’s
Lenz’s law
The direction of the induced EMF or current is always such as to oppose the change producing it