A-Level物理考试AS阶段的关键知识点

　　在A-level考试中，A-level物理是大家喜爱的一个理科课程，它的学习以理论和实操为主，那么今天小编就为大家介绍一下A-Level物理考试AS阶段的关键知识点，希望对大家有所帮助。

　　Measurement:

　　Random errorsare errorsof measurements in which the measured quantities differ from the mean valuewith different magnitudes and directions.

　　Systematic errorsare errors of measurements in which the measured quantitiesare displaced from the true value by fixed magnitude and in the same direction.Accuracyis ameasure of how close the results of an experiment agree with the true value.Precisionis ameasure of how close the results of an experiment agree with each other.

　　Kinematics:

　　Speed

　　is the rate ofchange of distance traveled with respect to time.

　　Velocity

　　is therate of change of its displacement with respect to time.

　　Acceleration

　　ofan object is the rate of change of its velocity with respect to time.

　　Forces And Dynamics

　　:

　　Normal contact force

　　is aforce perpendicular to the surface experienced by a body when it is in physicalcontact with something else.

　　Hooke’s Law

　　states that within the limit of proportionality, theextension produced in a material is directly proportional to the load applied.The

　　principle of moments

　　states that,when an object is in equilibrium, the sum of anticlockwise moments about anypoint equals the sum of clockwise moments about the same point.The

　　moment of a force

　　is the productof the force and the perpendicular distance between the axis of rotation andthe line of action of the force.A

　　couple

　　is a pair of forces, equalin magnitude but opposite in direction, whose lines of motion do not coincide.

　　Centre of gravity

　　is the point on an object through which the entire weight ofthe object may be considered to act.

　　Stability

　　ofan object refers to its ability to return to its original position after it hasbeen displaced from that position.

　　Pressure

　　isforce acting per unit area.

　　Upthrust/buoyancy force

　　is an upward force on a body produced by the surroundingfluid (i.e., a liquid or a gas) in which it is fully or partially immersed, dueto the pressure difference of the fluid between the top and bottom of theobject.

　　Archimedes’Principle

　　states that the upthrust experienced by an object partiallyor entirely immersed in a fluid is equal to the weight of the fluid displacedby the object.

　　Newton’s first law of motion

　　states that a body will continue in its state of rest oruniform motion in a straight line unless an external resultant force acts onit.

　　Newton’s second law

　　states that the rate of change of momentum of a body isproportional to the resultant force acting on it and the change takes place inthe direction of the force.

　　Newton’s third law

　　states that: If body A exerts a force on body B, then body Bexerts a force of equal magnitude but in the opposite direction on body A.The

　　principle of conservation of momentum

　　statesthat the total momentum of a system of objects remains constant provided noresultant external force acts on the system.

　　Work, Energy And Power

　　:

　　Work

　　is the mechanicaltransfer of energy to a system or from a system by an external force on it.

　　Heat

　　isthe non-mechanical transfer of energy from the environment to the system or fromthe system to the environment because of a temperature difference between thetwo.The

　　principle of conservation of energy

　　statesthat energy cannot be created nor destroyed in any process.

　　GravitationalPotential Energy

　　is defined as the amount of work done in order to raise thebody to the height h from a reference level.

　　Power

　　isdefined as the rate of work done or energy converted with respect to time.

　　Waves

　　:

　　Displacement

　　is thedistance moved by the particle from its equilibrium position.

　　The

　　amplitude

　　of a wave is the maximumdisplacement of the particle from its equilibrium position.The

　　wavelength

　　is the distance between2 successive points on a wave which are in phase with one another.The

　　period

　　is the time taken for aparticle on the wave to complete one oscillation.The

　　frequency

　　of a wave is the numberof complete oscillations that pass through a given point in 1 second. (Units:Hertz(Hz) or s-1)A

　　compression

　　is a region whereparticles are close to one another. (High pressure)A

　　rarefaction

　　is a region where theparticles are further apart. (Low pressure)

　　PhaseDifference

　　(φ) between two particles or two waves tells us how much aparticle (or wave) is in front or behind another particle (or wave).

　　Intensity

　　of awave is the rate of transfer of energy per unit area perpendicular to thedirection of travel of the wave.

　　Superposition

　　:

　　Diffraction

　　refers to thebending or spreading out of waves when they travel through a small opening orwhen they pass round a small obstacle.The

　　Principle Of Superposition

　　statesthat when two waves of the same kind meet at a point in space, the resultantdisplacement at that point is the vector sum of the displacements that the twowaves would separately produce at that point.

　　Interference

　　refersto the superposing of two or more coherent waves to produce regions of maximaand minima in space, according to the principle of superposition.

　　Gravitation

　　:

　　Newton’s Law Of Universal Gravitation

　　statesthat every particle in the Universe attracts every other particle with a forcethat is directly proportional to the product of their masses and inverselyproportional to the square of the distance between them.

　　Gravitational field strength

　　at a point is defined as the gravitational force per unitmass acting on a mass placed at that point.

　　Gravitational potential energy

　　, U of a point mass m, in a gravitational field, is the work doneby an external force in bringing that point mass from infinity to that point.

　　Gravitational potential

　　at a point in a gravitational field is the work done perunit mass, by an external force, in bringing the mass from infinity to thatpoint.

　　Escape speed

　　is the minimum speed with which a mass should be projectedfrom the Earth’s surface in order to escape Earth’s gravitation field.

　　Current Of Electricity

　　:

　　Electric Current

　　is therate of flow of charge through a particular cross sectional area with respectto time.

　　The

　　potential difference

　　between twopoints in an electrical circuit is the electrical energy converted into otherforms of energy per unit charge passing from one point to the other.

　　Onevolt

　　is the potential difference between two points in anelectrical circuit when one joule of electrical energy is converted to otherform of energy as one coulomb of charge passes from one point to the other.

　　Ohm’sLaw

　　states that the ratio of the potential difference across aconductor to the current flowing through it, is a constant, provided that itsphysical conditions, such as temperature, remain constant.The

　　electromotive force

　　($\epsilon$)of a source is the energy converted from other forms to electrical per unitcharge delivered round a complete circuit.

　　Internalresistance

　　(r) of any real source is the resistance that charge movingthrough the material of the source encounters.

　　DC Circuits

　　:

　　Kirchhoff’s First Law

　　statesthat the total current entering a junction is equal to the total currentleaving the junction. OR The algebraic sum of currents at a junction is zero.

　　Kirchhoff’ssecond law

　　states that the net electromotive force around a closedcircuit loop is equal to the sum of potential drops around the loop. OR Thealgebraic sum of the changes in potential encountered in a complete traversalof a closed circuit loop must be zero.

　　Alternating Current

　　:

　　The

　　root-mean-square (r.m.s.) value of analternating current

　　is equivalent to the steady direct currentthat converts electrical energy to other forms of energy at the same averagerate as the alternating current in a given resistance.

　　Rectification

　　isthe process in which an alternating current is forced to only flow in onedirection.

　　Semiconductors

　　:Band gap

　　is the energy difference between top of valence band andbottom of conduction band. It is also a range of energy in a solid where noelectron states exist.An

　　intrinsic semiconductor

　　is a puresemiconductor crystal containing only one element or one compound.Extrinsicsemiconductors doped with donor impurities are called

　　n-type semiconductors

　　because theydonate an excess of negative charge carriers.

　　Quantum Physics & Lasers

　　:

　　Photoelectric Effect

　　is the emission of electrons from metal by electromagneticradiation.

　　Photoelectron

　　is used to indicate that the electron has been emitted when light falls on thesurface of a metal.The

　　work function

　　of a material isdefined as the minimum amount of the work necessary to remove a free electronfrom the surface of the material.

　　Threshold frequency

　　is the minimum frequency of an incident radiation requiredto just remove an electron from the surface of a metal.The

　　scanning tunnelling microsope

　　(STM)is a non-optical microscope which uses the concept of quantum tunnelling byelectrons to study surfaces of conductors or semi-conducors at the atomic scaleof about 2 Å or 0.2 nm.

　　关于A-Level物理考试AS阶段的关键知识点就为大家介绍到这里了，希望大家能够好好复习，提高化学备考能力，并且小编建议大家要好好积累词汇，这样才能顺利通过考试，如果还想了解更多关于alevel官方考试局、alevel考试时间的信息，可以在线咨询我们或添加客服微信kewo11！