Definitions Flashcards

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1
Q

Absolute Zero

A

The lowest possible temperature at which substances have the minimum internal energy

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2
Q

Acoustic Impedence

A

The product of the density of a substance and the speed of ultrasound in that substance

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3
Q

Aphelion

A

The furthest point from the sun in an orbit

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4
Q

Archimedes’ Principle

A

The upthrust of an object is equal to the weight of fluid displaced

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5
Q

Attenuation

A

The decrease in the intensity of electromagnetic radiation as it passes through matter or space

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6
Q

Brownian motion

A

The continuous random motion of small particles suspended in a fluid, visible under a microscope

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7
Q

Chandrasekhar limit

A

The mass of a stars core beneath which the electron degeneracy pressure is sufficient to prevent gravitational collapse.
1.44 Solar masses

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8
Q

Coherance

A

Two waves sources, or waves, that are coherent have a constant phase difference

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9
Q

Cosmological principle

A

The assumption that the universe, when viewed on a large scale, is homogeneous and isotropic and the laws of physics applies everywhere

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10
Q

Coupling gel

A

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

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11
Q

Decay constant

A

The probability of a decay of an individual nucleus per unit of time

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12
Q

Faradays law

A

The magnitude of the induced EMF is directly praportional to the rate of change of flux linkage

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13
Q

Fundamental frequency

A

The lowest possible frequency at which an object can vibrate

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14
Q

Ideal gas

A

A model of a gas including assumptions similar to the behaviour of a real gas

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15
Q

Inelastic collision

A

A collision in which kinetic energy is transferred into other forms and is NOT conserved

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16
Q

Interference pattern

A

A pattern of constructive and destructive interference formed as waves overlap

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17
Q

Keplar’s First law of planetary motion

A

The orbit of a planet is an ellipse with the sun as one of the foci

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18
Q

Keplar’s Second law of planetary motion

A

A line segment connecting the planet and the sun sweeps out equal areas during equal intervals of time

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19
Q

Keplar’s Third law of planetary motion

A

The square of the orbital period is directly proportional to the cube of is average distance from the sun

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20
Q

Kirchoff’s First law

A

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

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21
Q

Kirchoff’s Second law

A

In a closed loop of an electrical circuit, the sum of the EMF’s is equal to the sum of the PD’s

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22
Q

Lenz’s law

A

The direction of the induced EMF or current is always such as to oppose the change producing it

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23
Q

Light Year

A

The distance travelled by light in a VACUUM in a time of one year

24
Q

Lost volts

A

The potential difference across the internal resistor of a source of EMF

25
Q

Internal resistance

A

The resistance of a source of EMF due to its construction which causes a loss in energy/voltage as the charge passes through the source

26
Q

Magnetic field lines

A

Lines of force drawn to represent a magnetic field pattern

27
Q

Magnetic flux

A

The product of the component of the magnetic flux density perpendicular to a given area and that cross-sectional area.
ø = BACosθ

28
Q

Magnetic flux density

A

The strength of a magnetic field

Defined by the equation B = F/IL

29
Q

Magnetic flux linkage

A

The product of the number of turns in a coil N and the magnetic flux

30
Q

Maxwell - Boltzmann distribution

A

The distribution of the speeds of a particles in a gas

31
Q

Newtons first law of motion

A

A body will remain at rest of continue moving at a constant velocity unless acted upon by a resultant force

32
Q

Newtons Second Law of Motion

A

The rate of change of momentum is directly proportional to the resultant force and takes place in the direction of the force

33
Q

Newtons Third Law

A

When two objects interact, each exerts and equal but opposite force and takes place in direction of the force

34
Q

Newtons Laws of gravitation

A

The force between two point masses is directly proportional to the product of the masses and inversely proportional to the square of the separation between them

35
Q

Ohm’s Law

A

The potential difference across a conductor is directly proportional to the current in the component as long as its temperature remains constant

36
Q

Parallax angle

A

The angle of the apparent shift in the position of a relatively close star against the backdrop of much more distant stars as the earth makes half a rotation of the sun

37
Q

Parsec

A

The distance at which the radius of one AU subtends an angle of one arcsecond

38
Q

Perihelion

A

The closest point to the sun in an orbit

39
Q

Phase difference

A

The difference between the displacements of particles along a wave
Or the difference between the displacements of particles on different waves
Measured in degrees or radians

40
Q

Plane Polarised

A

Description of a transverse wave in which the oscillations are limited to only one plane

41
Q

Resonance

A

The increase in amplitude of a forced oscillation when the driving frequency matches the natural frequency of oscillating system.

42
Q

Semiconductor

A

A material with a lower number density than a typical conductor

43
Q

Specific latent heat

A

The energy required to change the phase per unit of mass while at a constant temperature

44
Q

Stellar parallax

A

A technique used to determine the distance of stars that are relatively close to the earth by comparing their apparent positions against distant stars at times 6 months apart

45
Q

Threshold Voltage

A

The minimum potential difference at which a diode begins to conduct

46
Q

Wave-particle duality

A

A theory that states that matter has both particle and wave properties and also electromagnetic radiation has wave and particulate nature

47
Q

Wein’s Displacement Law

A

The peak wavelength (λmax) at which the radiation of a black body is a maximum, is inversely proportional to the absolute temperature of the black body.

48
Q

Youngs Modulus

A

The ratio of the tensile stress to tensile strain when these quantities are directly proportional to each other

49
Q

Binding energy

A

The minimum energy required to completely separate a nucleus into its constituent protons and neutrons

50
Q

Black body

A

An idealised object that absorbs all the electromagnetic radiation incident on it and when in thermal equilibrium emits a characteristic distribution of wavelengths at a specific temperature

51
Q

Gravitational Field

A

A field created around any object with mass, extending to infinity, but diminishing as distance from the centre of mass of the object increase

52
Q

Gravitational field strength

A

The gravitational force exerted per unit of mass at a point within a gravitational field

53
Q

Gravitational potential

A

The work done per unit of mass to bring an object from infinity to a point in the gravitational field

54
Q

Gravitational potential energy

A

The capacity for doing work as a result of an objects position in a gravitational field

55
Q

Hooked law

A

The force applied is directly proportional to the extension of the spring unless the limit of proportionality is exceeded

56
Q

Hubbles constant

A

The gradient of a graph of a line of best fit for a plot of recessional speed against distance from the earth of other galaxies

57
Q

Hubbles law

A

The recessional speed of a galaxy is almost directly proportional to its distance from Earth