O Level Combined Science Physics, 5076
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The List of Definitions
1. Physical Quantities, Units and Measurement
Physical quantity—A physical quantity is a measurable quantity and it comprises of a numerical magnitude and an associated unit.SI Units—It is the world’s most widely used system of measurement for Physical Quantities in agreement.Base of Fundamental Units—These units are from a set of physical quantities that seem to be independent of each other.Derived Units—These units are are obtained using the product or quotient of the base units.Scalars—A physical quantity that can be fully described / expressed by magnitude and an unit.Vectors—A physical quantity that can only be fully described / expressed with the added information of direction.Matter—Anything that has mass and occupies volume.Mass—A measure of the amount of substance in a body.Weight—A measure of the pull (force) due to gravity on a body/mass.Volume—The amount of space occupied by a body.Parallax Errors—Errors in measurement due to the eye not being vertically above a graduation mark.Zero Errors—Errors in measurement when a non-zero reading is obtained when there should be a reading of zero.
II. Newtonian Mechanics
Distance—The length covered along the path taken.Speed—The distance traveled per unit time.Average Speed—Total distance divided by total time, including rest.Displacement—Distance moved in a specific directionVelocity—Displacement moved with respect to time [or] Rate of change of displacementAcceleration—Change in velocity with respect to time [or] Rate of change of velocity.Terminal Velocity—The constant velocity which is eventually reached by a moving object when the driving force and the resistive forces are equal i.e. zero resultant force.
Resultant Force—The effective force acting on an object after vector analysis [or] The product of the mass and its acceleration.
4. Mass, Weight and Density
Mass—A measure of the amount of substance in a body.Weight (Gravitational Force)—A measure of the pull (force) due to gravity on a body/mass.Volume—The amount of space occupied by a body.Density—The mass per unit volume.Gravitational Field—The region around an object where the gravitational force due to it acts.Gravitational Force (Weight)—It is the pull (force) due to gravity on a body/mass.Gravitational Field Strength—It is the gravitational force per unit mass acting on a mass that is in a gravitational field.
5. Turning effect of Forces
Moment of a Force—The turning effect produced by a force about a pivot and it given by the product of the force and the perpendicular distance between the line of action of the force and the pivot.Principle of Moments—States that when a system (or body) is in rotational equilibrium the total clockwise moment about a pivot is equal to the total anti-clockwise moment about the same pivot.
Pressure—The force acting per unit area.
7. Energy, Work & Power
Energy—Energy is the ability to do work.Work Done—Work is said to be done or carried out when the point of application of a force has a displacement in the direction of the force.Power—The rate at which work is done [or] energy converted per unit time.Kinetic Energy—The energy possessed by a moving object by virtue of its speed/velocity.Gravitational Potential Energy—The energy possessed by an object by virtue of its height above the ground.Elastic Potential Energy—The energy in a compressed or stretched spring.Chemical Potential Energy—The energy that is stored in the bonds of chemical substances.Principle of Conservation of Energy—States that energy cannot be created nor destroyed but can be converted from one form to another.
III. Thermal Physics
8. Kinetic Model of Matter
Kinetic Model of Matter—The kinetic model of matter states that matter is made up of tiny particles called atoms and they are always in continuous, random motion. Their kinetic and potential energies depend on temperature and pressure.Brownian Motion—It is the random motion of particles suspended in a fluid (liquid and gas) due to collision with the fluid’s own atoms, molecules or ions.Pressure of a gas—It’s the force acting per unit area of contact with the gas due to its particles rate of collision with the container.Solid, Liquid and Gas—The three states which matter can be in based on temperature and pressure….…… (for now!)
9. Transfer of Thermal Energy
Conduction—It is the method of transfer of thermal energy in solids whereby when thermal energy is supplied, the particles vibrate more vigorously about their fixed positions and transfer this energy to the neighbouring particles which have less thermal energy.Convection—It is the method of transfer of thermal energy in fluids (liquids and gases) by the motion of particles due to density changes.Radiation—It is the method of transfer of thermal energy in vacuum, in the absence of matter.Thermal Equilibrium—An object or a system of objects is said to be in thermal equilibrium when the net thermal energy transfer is zero. i.e. the energy flowing out should equal energy flowing in.Convectional Current—The movement of particles in a fluid due to different densities arising from difference in temperatures sets up what is called a convectional current.
10.Thermal Properties of Matter
Melting—Change of state of matter from solid to liquid at a fixed temperature called the melting point.Vaporisation/Boiling—Change of state of matter from liquid to gas at a fixed temperature called the boiling point.Sublimation—Change of state from solid to liquid without going through liquid state.Evaporation—Change of state from liquid to gas below the boiling point. And happens at the liquid surface as most energetic particles escape into gaseous state.
11. General Wave Properties
Wave—Transfer of energy without transfer of matter by means of vibration.Transverse waves—Waves whose direction of vibration is perpendicular to direction of wave motion.Longitudinal waves—Waves whose direction of vibration is parallel to direction of wave motion.Amplitude—The maximum displacement from the equilibrium position.Wavelength—The length of one complete wave.Period—The time taken for one complete oscillation or wave to pass through/generated.Frequency—The number of waves passing through/generated per unit time.Wavefront— An imaginary line joining the part of the wave which are in phase or in same state of vibration at that point in time.Crest—Highest point on the wave, which results in the amplitude.Trough—Lowest point on the wave, which results in the amplitude.Compressions—High pressure regions in a sound wave that are formed when particles on either sides of that point converge.Rarefactions—Low pressure regions in a sound wave that are formed when particles on either sides of that point diverge.
Normal—The imaginary line perpendicular to the plane on which the light rays hits. It is the line from which the angle of incidence, angle of reflection and angle of refraction are measured.Refraction—The bending of light when it travels from one medium into another of different density at the boundary of the two mediums is called refraction.Refractive Index—The ratio of the sines of the angle in vacuum to that in the medium (from the Normal) [or] The ratio of the speed of light in vacuum to that in the medium.Total Internal Reflection—The phenomenon that happens when the incident rays are completely reflected into the same medium when light travels from more dense to less dense medium.Critical Angle—The angle of incidence for which the angle of refraction is 90o as light travels from a dense medium to a less dense medium.Converging Lens—They converge incoming light rays which are parallel to the principle axis to a point, called the focal point.Focal Point—The point on the principle axis on which the incoming parallel light rays are converged (focused) to.Focal Length—The distance between the lens axis and the focal point is called the focal length.Real Images—These are images that can be projected or focused onto a screen due to the converging nature of the light rays emitting from the object.Virtual Images—These are images that cannot be projected onto a screen, formed on plates or films due to them diverging from a point. Often they are on the same side as the object and hence cannot be projected.
13. Electromagnetic Spectrum
EM Waves—Transverse waves with a range of different frequencies and wavelenght but same velocity that has both electrical and magnetic components oscillating perpendicular to each other.
Compressions—High pressure regions in a sound wave that are formed when particles on either sides of that point converge.Rarefactions—Low pressure regions in a sound wave that are formed when particles on either sides of that point diverge.Echo—The reflection of sound waves off of a boundary.Loudness—Refers to the physical strength of a sound wave and quantified by its amplitude.Pitch—Refers to the sharpness of the sound and quantified by its frequency.
V. Electricity and Magnetism
15. Static Electricity
16. Current of Electricity
Coulomb—The unit of charge.Current—The rate of low of electrical charge at a point.Potential Difference PD—The potential difference across two points in a circuit is the work done to drive a unit charge between them.Electromotive Force EMF—The e.m.f of an electrical source is the work done by the source in driving a unit charge round the complete circuit.Resistance—Resistance is the opposition to current given by the ratio of the p.d across the component to the current flowing through it.Power—Electrical energy dissipated/used per unit time.Ohm’s Law—Ohm’s law states that the current through a conductor between two points is directly proportional to the potential difference across the two points.Ohmic conductor—An ohmic conductor has a linear relationship between voltage and current. i.e. the resistance is constant.
17. DC Circuits
18. Practical Electricity
Unit of Electrical Energy, KWhr—The unit of electrical energy commonly used in the market place.Switch—A device to open/close the electrical circuit.Fuse—A device that melts and opens the circuit when a current higher than its rated flows through it.Circuit Breaker—An electromechanical device that opens the circuit when a current higher than its rated flows through it.Earthing—To physically connect the ground (earth) to parts of the electrical appliances for safety.Double Insulation—A safety implementation where the metal parts that can conduct electricity are not exposed and are insulated by at least two layers of non-conductors such as plastics.Short Circuit—An electrical charge flow due to lower resistance often bypassing the intended circuit.
19. Magnetism & Electromagnetism
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