A水準(zhǔn)物理專業(yè)術(shù)語(GlossaryoftermsusedinA-LevelPhysics))

1、Glossary of terms used in A-LevelPhysicsAbsolute zero of temperature：the lower fixed point on the thermodynamic scale of temperature; it is considered to be the lowest possible temperatme in the universe.Absolute scale of temperature：a theoretical temperature scale that does not depend on the thermo

2、metric property of a material.Acceleration： the rate of change of velocity with respect to time. It has the SI units of ms,Acceleration of free fall：the rate of change of velocity of an object when it falls freely towards the Earths surface under the sole influence of me gravitational pull of me Ear

3、th. It is denoted by the symbol g and has a numerical value of 9.81 ms.Accuracy：the proximity of the observed reading on an instrument to the true or actual value of the physical quantity being measured.Ammeter：an electrical instrument that measures the electric current in a circuit.Amount of substa

4、nce： the number of moles of a substance (see moles).Ampere： the constant current that exerts a force of 2N per metre length on two straight, parallel and infinitely long wire of negligible cross-sectional area when that current flows through the two wires. It is the SI unit of an electric current an

5、d is represented by the symbol A.Amplitude： the maximum displacement from the equilibrium position to the crest or trough of a sinusoidal wave.Angular displacement： the angle through which a rotating axis turns. It is usually measured in radians.Angular velocity： the rate of change of angular displa

6、cement with respect to time, It is measured in rad s.Anode：positive electrode.Antinodes：points of maximum displacement in a stationary wave.Atmosphere： a unit of pressure equal to 1.01 Pa or 760mmHg.Atmospheric pressure： the pressure at a point due to the weight of the air column above it.Atom： the

7、smallest part of an element that can exist naturally.Atto： a prefix used in the metric system of units to denote a sub-multiple of .Avogadro constant: the number of atoms in exactly 0.012 kg of carbon-12 and has a numerical value of 6.02 mol. It is denoted by or .Barometer: a device that measures at

8、mospheric pressure-Base quantity; one of the seven arbitrarily chosen physical quantities that is used to define other physical quantities in the SI system.Base unit: a unit of base quantity that is used to define the SI units of other physical quantities.Boiling: the process in which a liquid chang

9、es into vapour at a definite temperature.Boiling point: the temperature of a liquid as it changes into the gaseous state when the saturated vapour pressure of the liquid equals to the external pressure acting on it.Boltzmann constant: the ratio of the molar gas constant R to the Avogadro constant .B

10、oyles law: the pressure () of a given mass of gas at constant temperature is inversely proportional to its volume ().Brownian motion; the continuous and random movement of tiny microscopic particles suspended in a fluid.Cathode Ray Oscilloscope (CRO): an electronic instrument that uses the cathode r

11、ay tube to convert electrical signals into a displacement-time graph on the CROs screen from which essential information such as amplitude and the period of a signal could be measured.Cathode: negative electrode.Celsius scale of temperature: a scale of temperature that is adjusted to agree with the

12、thermodynamic scale of temperature.Centi: a prefix used in the metric system to denote sub-multiple of .Centigrade scale of temperature: an empirical scale of temperature in which the lower and upper fixed points are the freezing and boiling point of water respectively.Centre of gravity: the single

13、point in a body through which the entire weight of that body appears to act.Centre of mass: the single point in a body through which the entire mass of that body appears to act.Centripetal acceleration: the acceleration of a moving object that is always directed towards the centre of the circular pa

14、th on which the object is travelling.Centripetal force: the force on a moving object that is always directed towards the centre of the circular path on which the object is travelling.Charles law: the volume (V) of a fixed mass of gas at constant pressure is directly proportional to its thermodynamic

15、 temperature (T).Compression: a region of higher pressure in a medium.Compressive forces: two equal but oppositely directed forces acting on an object that reduces it length-Coherent sources: two sets of waves that have a constant phase difference; have the same frequency and wavelength and are not

16、polarised.Condensation: the process whereby a substance in the vapour state changes into the liquid state.Conditions of equilibrium for forces acting on a body: (1) the vector sum of all forces acting on a rigid body must be zero.(2) the vector sum of all external torques acting on a rigid body must

17、 be zero.Conduction (thermal): the transmission of heat from a region of higher temperature to a region of lower temperature through collision of particles within that medium.Conductor (electrical): a material that allows the free movement of electric charges.Conservation of energy: energy cannot be

18、 created or destroyed but can be changed from one form to another.Conservation of linear momentum: the total momentum of a closed system of colliding particles remains constant if no external forces act on that system.Constructive interference: the interaction of two or more waves at a point such th

19、at the amplitude of the resultant wave is greater than the amplitude of the individual waves.Convection: the transmission of heat from a region of higher temperature to a region of lower temperature through the movement of heated fluid.Coulomb: the charge flowing pass a point in a electric circuit d

20、ue to the passage of one ampere of electric current flowing for one second. It is the SI unit of an electric charge and is represented by the symbol C.Couple: two equal and oppositely directed parallel forces that do not lie on the same line of action. Crest: the highest point on a wave.Critical dam

21、ping: a system that does not oscillate but returns to the equilibrium position in the shortest possible time.Current (electric): the rate of flow of charge with respect to time.Damped oscillations (light): a system which oscillates about the equilibrium position with deceasing amplitude over a perio

22、d of time.Deceleration: the decrease of velocity of an object. Density: mass per unit volume of a substance.Destructive interference: the interaction of two or more waves at a point such that the amplitude of the resultant wave is smaller than the amplitude of the individual waves.Diffraction: the s

23、preading or bending of waves at the edge of an obstacle or when waves pass through an aperture.Diffraction grating; a device made of glass or transparent plastic that produces line spectra when light passes through hundreds of parallel and equally spaced lines ruled on it.Diffusion: the process by w

24、hich different gases or liquids mix as a result of rapid and random spreading of their component atoms, molecules or ions.Displacement: the distance moved in a specific direction.Drag forces: the frictional forces experienced by an object when it moves through a fluid or when the fluid flows pass th

25、e object.Dynamics: the study of forces and energies that are associated with the motion of a body.Elastic collision: a collision in which the total kinetic energy and momentum of the colliding bodies are conserved.Elasticity: the property of a material that enables it to return to its original shape

26、 and dimensions when the applied stress is removed.Elastic constant: a constant of proportionality that is numerically equal to the ratio of the applied force to the extension of an elastic material.Electromagnetic spectrum: a wide range of electromagnetic waves arranged in ascending order of wavele

27、ngths.Electromagnetic waves: transverse waves consisting of electric and magnetic fields that oscillates perpendicularly to each other.Electron: an elementary particle with a rest mass () of 9.11 kg and elementary charge () of 1.60C.Electron diffraction: the spreading of electrons to form a pattern

28、of rings on a screen as it passes through a thin gold foil or crystalline material.Electric charge: the smallest quantity of discrete charge carried by an electron. It has the symbol e and has a value of 1.60CEmpirical scale of temperature: a temperature scale based on the linear variation of a ther

29、mometric property with temperature.Energy: a measure of the stored ability within a system or body to do work, It has the SI unit of joules (J).Equations of motion: a set of equations that relates the displacement , initial velocity , final velocity , acceleration and time,Equilibrium (thermal): see

30、 thermal equilibrium.Escape velocity: the velocity that a body must be given on the surface of a planet in order for it to just escape from the gravitational pull of that planet.Experimental error: the difference between a value obtained through experiments and the true value.Evaporation: the proces

31、s by which energetic molecules leave the surface of a liquid to form vapour or gas.Fixed point: a temperature at which a reproducible and measurable physical change occurs.First law of thermodynamics: the heat transferred to a closed system increases its internal energy All and causes the system to

32、do work AW on its surroundings during the change.Fluid: a liquid or a gas.Force: a physical quantity that can change the shape of an object, the direction of its motion and its acceleration.Forced oscillations: oscillations produced when a body is subjected to an oscillatory external force.Free fail

33、: the motion of a body through a gravitational field whereby the only force acting on it is its weight.Free body diagram: a force diagram that shows all forces acting on a single body without including its surroundings or environment.Freezing: the process in which a liquid changes into a solid witho

34、ut a change in temperature.Frequency: the number of oscillations or vibrations per second.Friction: a force that tends to prevent or oppose motion between two objects in contact.Gas: a state of matter in which molecules move with large random velocities and are separated from each other with large i

35、ntermolecular distances.Gravitation: the mutual attraction between masses.Gravitation field: a region of space where the effects of gravitational force is experienced by a mass.Gravitational field strength at a point: the force on a unit mass placed at a point in a gravitational field.Gravitational

36、potential at a point: the work done in bringing a unit mass from infinity to a point in a gravitational field.Gravitational potential difference between two points: the work done in bringing a unit mass from one point to the other in a gravitational field.Hall probe: an electronic instrument that us

37、es the Hall effect to measure magnetic field strength. Heat: the thermal energy that flows from a region of higher temperature to a region of lower temperature.Heavy damping: a system that do not oscillate and will take a long time to reach the equilibrium position due to large frictional or resisti

38、ve force acting on it.Heat capacity: the amount of heat required to raise the temperature of the entire body by one degree kelvin. The SI unit is Joules per kelvin (JK) and its symbol is C.Heat transfer: the process where thermal energy flows away from a body through thermal conduction, convection a

39、nd radiation.Hertz: the SI unit of frequency.Hookes law: force is directly proportional to the extension in a spring or wire if the limit of proportionality is not exceeded.Homogeneity: the necessary condition that validates a physical equation by requiring all units of the physical quantities on th

40、e left- and right-hand side of the equation to be the same.Ice point: the equilibrium temperature of a mixture of pure ice and water at standard atmospheric pressure.Ideal gas: a hypothetical gas made up of a large number of small molecules that moves randomly and collides elastically with each othe

41、r and obeys the ideal gas laws.Ideal gas law: an equation that describes the state of an ideal gas and has the following form: where p = pressure of the gas; n = number of moles; V = volume of the gas; R = molar gas constant；T = temperature of the gas in kelvins.Impulse: the product of the force ()

42、acting on a body and the time interval (t) over which the force acts.Inelastic collision: a collision in which linear momentum is conserved but kinetic energy is not conserved,Inertia: a measure of the resistance to changes in motion of a body.Infrared: an electromagnetic wave of wavelength to m in

43、the electromagnetic spectrum. Insulator (electrical): a material that do not allow electric charges to flow through easily.Instantaneous acceleration: acceleration at a particular time. Instantaneous velocity: velocity at a particular time.Intensity (of a wave): the rate of How of energy per unit ar

44、ea perpendicular to the direction of the wave.Internal energy (of a thcrmodynamic system): the sum total of the kinetic and potential energies of all atoms and molecules in that system.Interference: the superposition of two or more wavetrains from coherent sources to form a new wave pattern.Joule: t

45、he work done when a force of one newton moves its point of application a distance of one metre in the direction of the applied force. It has the SI unit of newton metre.Kelvin: the fraction 1/273.16 of the temperature difference between absolute zero and the triple point of water. It is the SI unit

46、of thermodynamic temperature.Kilo: the prefix used to indicate the multiple of 103 of any units. It has the symbol of k.Kinematics: a branch of mechanics that describes the motion of a particle without reference to the force or energy that causes the motion.Kinetic energy: the energy possessed by a

47、mass due to its motion. It is a scalar quantity.Kinetic theory of gases: A theory describing the physical properties of gases through the application of Newtons laws of motion on colliding gas molecules and offers an explanation on why gases obey the gas laws.Lift: the upward force exerted on an aer

48、oplane caused by air flowing over the upper and lower wings of a moving plane at different speeds.Limit of proportionality: the point on a stress-strain curve at which the line changes from being linear (straight line) to non-linear (a curve).Linear momentum (of a body): the product of mass and velo

49、city of the bodyLiquid: a fluid in which molecules are not bounded in a rigid structure but each molecule is free to move through the body of the fluid and still maintain close proximity with other neighbouring molecules.Longitudinal waves: progressive waves in which the direction of vibrations of p

50、articles in the wave is along the line of flow of energyManometer: a mercury-filled U-tube that is used to measure the pressure difference of a fluid.Mass: a measure of a bodys resistance to changes in motion. It is a base quantity with the, SI unit of kilogram.Mean square speed: the average value o

51、f the square of the molecular speeds.Measurement: the comparison of a physical quantity with a calibrated measuring instrument in order to associate that physical quantity with a magnitude.Measurement error: see experimental error.Microwaves: electromagnetic waves with wavelengths that range from ab

52、out 1 mm to about 10cm.Molar mass: the mass of one mole of a substance.Mole: the SI base unit for the amount of substance.Moment of a force (about a point): the product of the force and the perpendicular distance from the line of action of the force to the point.Newton: the force which produces an a

53、cceleration of 1 ms when it is applied to a mass of one kilogram.Newtons first law of motion: an object at rest will remain at rest and an object in motion will continue in motion at constant speed in a straight line in the absence of a resultant force.Newtons second law of motion: the rate of chang

54、e of momentum of an object is directly proportional to the resultant force acting on that object and has the same direction as the force.Newtons third law of motion: action and reaction are always equal but oppositely directed on two different bodies.Newtons law of gravitation: a point mass will att

55、ract another point mass in any part of the universe with a force that is directly proportional to the product of the masses and inversely proportional to the square of the distance between them.Node: a point on a stationary wave where the amplitude of oscillation is zero.Parallax error: arises when

56、the eye is not positioned vertically above the scale to be measured.Parallelogram law of vector addition: the resultant of two vectors acting at a point P is represented by the diagonal of a parallelogram formed by the two vectors and its origin is at F.Path difference: the extra length travelled by

57、 a wave when it is compared with another.Period: the time taken to generate a complete wave or to complete one oscillation of a vibrating system.Phase (of a particular point in an oscillation): the fraction of the oscillation measured from an initial chosen point and expressed in degrees () or radia

58、ns (rad).Phase difference: a measure of the extent to which a wave is out of phase with a reference wave and expressed in degrees () or radians (rad). Physical quantities: quantities that are measurable and can be expressed as a numerical value and an acceptable standard or unit.Pitch: the frequency

59、 of a sound wave.Plastic deformation: the permanent change In structure of a material and the corresponding drastic change in shape and size when the material is subject to stress that is close to its breaking value,Potential energy in a system: the energy stored by virtue of its position, shape, co

60、nfiguration or state of the system.Power: rate of work done or energy transfer.Pressure: the force acting perpendicularly per unit area.Pressure law: the pressure of a fixed mass of gas at constant volume is directly proportional to the absolute scale of temperature.Principle of moment: the sum of t