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165 Cards in this Set
- Front
- Back
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Acceleration |
The rate of change of velocity, a vector quantity |
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Acceleration of freefall |
The rate of change of velocity of an object falling in a gravitational field, symbol g |
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Air resistance |
The drag or resistive force experienced by an object moving through air opposing the direction of motion |
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Ammeter |
A device used to measure electric current- it must be placed in series and ideally have zero resistance |
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Ampere |
The current flowing through two parallel wires in a vacuum 1m apart such that there is an attractive force of 2*10^-7 per metre length of wire between them or one coulomb of charge going past a point in one second |
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Amplitude |
The maximum displacement from the equilibrium position |
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Angle of incidence |
The angle between the direction of travel of a incident wave and the normal at a boundary between two media |
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Angle of reflection |
The angle between the direction of travel of the reflected wave and the normal at a boundary of two media |
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Anion |
A negatively charged ion. They are attracted to the anode |
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Anode |
A positively charged electrode |
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Antiparallel |
In the same line but opposite directions |
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Antiphase |
Particles oscillating completely out of step with each other (one reaches maximum positive displacement when the other reaches maximum negative displacement) |
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Archimedes principle |
The upthrust acting on an object that is fully or partially submerged is equal to the weight of the fluid it diplaces |
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Average speed |
The rate of change in distance over a complete journey |
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Average velocity |
The change in displacement for a journey divided by the time taken |
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Base unit |
One of the seven units that for the building blocks of the SI measurement system, (metres, seconds, amperes, kelvin, kilograms, candelas and mols |
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Battery |
A collection of cells that transfers chemical energy into electrical energy |
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Braking distance |
Distance travelled by a vehicle from the time the brakes are applied until the vehicle stops. Affected by: speed, road conditions, tyres, brakes, no of people in car |
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Breaking strength |
The stress value at the point of fracture, calculated by dividing the breaking force by the cross sectional area |
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Centre of mass |
A point through which any externally applied force produces straight line motion but no rotation |
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Charge carrier |
A particle with charge that moves through a material to form an electric current e.g. electron in a wire |
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Closed system |
An isolated system that has no interaction with its surroundings |
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Coherence |
Two wave sources or waves that have a constant phase difference |
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Component |
One of the two perpendicular vectors obtained by resolving a vector |
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Compression (waves) |
A moving region in which the medium is denser or has higher pressure than the surrounding medium |
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Compression |
The decrease in length of an object when a compressive force is applied |
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Compressive deformation |
A change in the shape of an object due to compressive forces |
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Compressive force |
Two or more forces together that reduce the length or volume of an object |
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Conservation of charge |
Electric charge can neither be created or nor destroyed- the total charge in any interaction must be the same before and after the interaction |
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Constant speed |
Motion in which the distance travelled per unit time stays the same |
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Constant velocity |
Motion in which the change in displacement per unit time stays the same |
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Constructive inference |
Superposition of two waves in phase so the resultant wave has a greater amplitude than the original waves |
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Conventional current |
A model used to describe electric current in a circuit - travels from positive to negative - it is in the direction that positive charges would travel |
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a coulomb |
1 coulomb of electric charge passes a point in 1s when there is an electric current of 1 A |
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Couple |
A pair of equal and opposite forces acting on a body but not in the same staright line (parallel) |
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Critical angle |
The angle of incidence at the boundary between two media that will produce an angle of refraction of 90 degrees |
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Crystallography |
A method for determining the structure of a substance by studying the interference patterns producd by waves passing though a crystal of a substance |
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de Broglie equation |
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Density |
The mass per unit volume of a substance |
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Destructive interference |
Superposition of two waves in antiphase so that the waves cancel each other out and the resultant wave has a smaller amplitude than the original waves |
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Diffraction |
The phenomenon in which waves passing through a gap or round an obstacle spread out. biggest when gap size similar to wavelength |
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Brittle |
Property of a material that does not show plastic deformation and deform very little at high stress |
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Capacitor |
A component that stores charge, consists of two plates separated by an insulator (dielectric) |
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Cathode |
A negatively charged electrode |
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Cation |
A positively charged ion, it is attracted to the cathode |
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Cell |
A device that transfers chemical energy into electrical energy |
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Centre of gravity |
An imaginary point at which the entire weight of an object seems to act |
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Diode |
A semiconductor component that allows current only in one particular direction |
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Displacement (waves) |
The distance from the equilibrium position in a particular direction |
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Drag force |
The resistive force exerted by a fluid on an object moving in it opposing the direction of motion |
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Ductile |
Property of a material that has a large plastic region in a stress-strain graph so can be drawn into wires |
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Efficiency |
The ratio of useful output of energy to total input of energy, often as a percentage |
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Elastic deformation |
A reversible change in the shape of an object due to a force- removal of stress force will return the object to its original shape and size |
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Elastic limit |
The force where elastic deformation turns into plastic deformation and the object no longer returns to its original shape and size when the force is removed |
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Elastic potential energy |
The energy stored in an object because of its deformation |
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Electric charge |
A physical property - either positive or negative measured in coulombs |
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Electric current |
The rate of flow of charge |
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Electrolyte |
A liquid containing ions that are free to move so conduct electricity |
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Electromagnetic spectrum |
The full range of frequencies of electromagnetic waves- radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays |
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Electromagnetic wave |
Transverse waves with oscillating electric and magnetic components - travel at 3*10^8 in a vacuum |
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Electromotive force (EMF) |
The work done on the charge carriers per unit charge |
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Electron gun |
A device that uses a large accelerating potential difference to produce a narrow beam of electrons |
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Electronvolt |
Energy transferred to or from an electron when it passes through a potential difference of 1V 1eV=1.6*10^-19J |
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Energy |
The capacity for doing work |
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Equilibrium |
A body is in equilibrium when the net force and net moments acting on it are zero |
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Equilibrium position (waves) |
The resting position for particles in the medium |
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Extension |
The increase in length of an object when a tensile force is exerted on it |
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Filament lamp |
An electric component containing a narrow filament of wire that transfers energy into heat and light |
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Fluid |
A substance that can flow e.g liquids or gases |
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Force |
A push or pull on an object |
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Force constant |
force divided by extension - measures stiffness |
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Free fall |
The motion of an object accelerating under gravity with no other force acting on it |
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Frequency (waves) |
The number of wavelengths passing a given point per unit time |
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Fundamental frequency |
The lowest frequency at which an object can vibrate |
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Gold leaf electroscope |
A device with a metallic stem and a gold leaf that can be used to identify and measure electric charge |
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Gravitational potential energy |
The capacity for doing work as a result of an object's positions in a gravitational field |
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Harmonic |
A whole number multiple of the fundamental frequency |
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Hooke's Law |
The force applied is directly proportional to the extension of the spring unless the limit of proportionality is exceeded |
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Impulse |
Area under under the force time graph The product of force and time for which the force acts The rate of change of momentum |
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In phase |
Particles oscillating perfectly in time with each other (reaching their max positive displacement at the same time) |
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Inelastic collision |
A collision where kinetic energy is lost |
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Intensity (waves) |
The radiant power passing through a surface per unit area |
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Interference |
Superposition of two progressive waves from coherent sources to produce a resultant wave with a displacement equal to the sum of the individual displacements from the two waves |
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Internal resistance |
The resistance of a source of EMF due its construction, which causes a loss in energy/ voltage as the charge passes through the source |
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kilowatt-hour |
1kWh= 3.6*10^6 J Quantity of energy converted into other forms of energy by a device of power 1kW in 1hour |
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Kinetic energy |
The energy associated with an object as a result of its motion |
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Kirchoff's 1st Law |
The sum of the current leaving a junction is equal to the sum of the currents entering it Charge is conserved It=It+It+It Q=Q+Q+Q |
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Kirchoff's 2nd Law |
In a closed loop of an electrical circuit, the sum of the EMF is equal to the sum of the PDs of the loops |
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Law of reflection |
The angle of incidence is equal to the angle of reflection |
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LDR- light dependant resistor |
Resistance decreases as the light intensity incident on it increases |
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LED -light emitting diode |
A type of diode that emits light when it conducts electricity |
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Limit of proportionality |
The value of force beyond which stress is no longer directly proportional to strain (stops following Hooke's law) |
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Longitudinal wave |
A wave in which oscillations of particles is parallel to the direction of the wave travel |
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Mean drift velocity |
The average velocity of electrons as they move through a wire |
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Moment |
The product of force and perpendicular distance from a pivot |
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Newton's 1st law of motion |
A body will remain at rest or continue to move at a constant velocity unless acted upon by a resultant force |
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Newton's 2nd law of motion |
The rate of change of momentum of an object is directly proportional to the resultant force and takes place in the direction of the force |
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Newton's 3rd law of motion |
When two objects interact, each exerts an equal but opposite force on each other during the interaction Every action has its equal opposite reactions |
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Node |
For a stationary wave, a point where the amplitude is always zero |
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Non-ohmic component |
Doesnt follow ohms law e.g filament bulb, diode |
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Normal contact force |
The force exerted by a surface on an object, which acts perpendicular to the surface |
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Number density |
The number of free electrons per cubic metre of a material |
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ohm |
The resistance of a component that has a potential difference of 1V per unit ampere |
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Ohm's Law |
The potential difference across a conductor is directly proportional to the current in the component as long as physical conditions remain constant |
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Out of phase |
Particles are neither in phase nor antiphase |
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Perfectly elastic collision |
A collision in which no kinetic energy is lost |
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Period (waves) |
The time taken for one complete wavelength to pass a given point |
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Phase difference |
The difference between the displacements of particles along a wave or on different waves |
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Photoelectric effect |
The emission of photoelectrons from a metal surface when electromagnetic radiation above the threshold frequency illuminates the metal |
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Photoelectrons |
Electrons emitted from the surface of a metal by the photoelectric effect |
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Photon |
A quantum of electromagnetic energy |
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Plane polarised |
A transverse wave that can only oscillate in one plane |
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Plastic deformation |
A irreversible change in the shape of an object due to compressive or tensile force |
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Polarisation |
The phenomenon in which oscillations of a transverse wave are limited to only one plane |
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Path difference |
The difference in the distance travelled by two waves from the source to a specific point |
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Polymeric |
Material with long chain molecules e.g. rubber |
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Potential difference |
Energy transferred from electrical to other forms per unit charge |
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Potential divider |
An electrical circuit designed to divide to potential difference across two or more components in order to produce a specific output |
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Power |
The rate of work done |
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Pressure |
The force exerted per unit cross sectional area |
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Principle of conservation of energy |
The total energy of a closed system remains constant- energy cannot be created or destroyed |
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Principle of conservation of momentum |
Total momentum of a closed system remains the same before and after a collision |
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Principle of moments |
For a body in rotational equilibrium, the sum of the anticlockwise moments about a point is equal to the sum of the clockwise moments about the same points |
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Principle of superposition of waves |
When two waves meet at a point the resultant displacement is the sum of the displacements of the individual waves |
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Progressive wave |
A wave that transfers energy from one place to another |
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Rarefraction (waves) |
The part of the longitudinal wave when particles are less dense |
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Reflection |
The change in direction of a wave at a boundary between two different media, so the wave remains in the same medium (wave bounces) |
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Refraction |
The change in direction of a wave as it changes speed when it passes from one medium to another less > more bend TOWARDS the normal |
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Refractive Index |
The refractive index of a material n=c/v |
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Resistance |
A property of a component R=V/I |
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Resistivity |
A property of a metal that depends on resistance, cross sectional area and the length of wire |
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Resistor |
An component that obeys Ohm's law, transferring electrical energy into thermal |
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Restoring force |
A force that tries to return a system to its equilibrium position |
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Semiconductor |
A material with a lower number density than a typical conductor |
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Stationary/ Standing wave |
A wave that remains in a constant position with no net energy transfer and is characterised by nodes and antinodes |
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Stiffness |
The ability of an object to resist deformation |
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Stopping distance |
The total distance travelled from the time when a driver first sees a reason to stop to the time when the vehicle stops sum of thinking and braking distance |
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Tension |
The pulling force exerted by a string, cable or chain on an object |
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Terminal p.d |
The potential difference across the power source- when there is no current this is equal to the EMF of the source but if there is current, it is equal to the EMF minus the lost volts |
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Terminal velocity |
The constant velocity reached by an object when the drag force (and upthrust) is equal to the opposite weight of the object |
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Thermionic emission |
The emission of electrons from the surface of a hot metal wire |
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Thermistor |
An electric component that has a resistance that decreases when temperature increases |
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Thinking distance |
The distance travelled by a vehicle from when the driver first sees a reason to stop to when the brakes are applied |
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Threshold frequency |
The minimum frequency of the electromagnetic radiation that will cause the emission of an electron from the surface of a metal |
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Threshold voltage |
The minimum potential difference at which a diode begins to conduct- 0.7V |
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Timebase |
The time interval represented by one horizontal square on an oscilloscope screen |
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Torque (of a couple) |
The product of one of the forces of a couple and the perpendicular distance between the forces |
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Total internal reflection |
The reflection of all light hitting a boundary between two media back into the original medium, when the light is travelling through the medium with the higher refractive index and the angle of incidence at the boundary is greater than the critical angle |
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Transverse wave |
A wave in which the oscillations of medium particles are perpendicular to the direction of travel of the wave |
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Ultimate tensile strength |
The max stress that a material can take before it breaks |
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Uniform gravitational field |
A gravitational field in which field lines are parallel and the value of g remains constant |
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Unpolarised |
A transverse wave in which the oscillations occur in many planes |
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Upthrust |
The upward buoyant force exerted on a body immersed in a fluid |
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Velocity |
A vector quantity equal to the rate of change of displacement |
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Volt |
Energy transferred per unit charge. 1V is pd across a component when 1J of energy is transferred per 1C passing through the component |
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Voltmeter |
A device used to measure potential difference- it must be placed in parallel ideally with infinite resistance |
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Wave speed |
The distance travelled by the wave per unit time |
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Wave front |
A line of points in phase with each other in a wave, perpendicular to the direction of energy transfer |
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Wavelength |
The minimum distance between two points oscillating in phase e.g. peak to peak or trough to trough |
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Wave-particle duality |
Theory that states that matter has both particle and wave properties |
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Weight |
Gravitational force on an object |
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Work |
The product of force and the distance moved in the direction of the force |
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Work function |
The minimum energy needed to remove one electron from the surface of a metal |
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Yield point |
A point on a stress strain graph beyond which deformation is no longer entirely elastic |
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Young's Modulus |
Stress/strain |
