Year 12 physics definitions topic order Flashcards
Fiducial mark
An object placed in the field of view for an observer to use as a reference point.
Anomalous value
An anomalous value in a set of results is one that does not fit the overall trend in the data. it is therefore discounted from any analysis.
Random error
Random errors give values that are scattered randomly above and below the true value when the measurement is repeated. Taking a mean of repeated values obtains a better result.
Accuracy
Accuracy is a measure of the closeness of agreement between an individual test result and the true value. If a test result is accurate, it is in close agreement with the true value.
Error
Error (of measurement) is the difference between an individual measurement and the true value (or accepted reference value) of the quantity being measured.
Precision
Precision is the closeness of agreement between independent measurements obtained under the same conditions. It depends only on the distribution of random errors (i.e. the spread of measurements) and does not relate to the true value.
Repeatability
Repeatability is the precision obtained when measurement results are produced over a short timescale by one person (or the same group) using the same equipment in the same place.
Reproducibility
Reproducibility is the precision obtained when measurement results are produced over a wider timescale by different people using equivalent equipment in different (but equivalent) places.
Resolution
Resolution is the smallest change in the quantity being measured that can be detected by an instrument.
Uncertainty
Uncertainty is an estimate attached to a measurement which characterises the range of values within which the true value is asserted to lie. This is normally expressed as a range of values such as 44.0 ± 0.4.
Valididty
Validity can apply to an individual measurement or a whole investigation. A measurement is valid if it measures what it is supposed to be measuring. An investigative procedure is valid if it is suitable to answer the question being asked.
Systematic error
A systematic error is one that doesn’t happen by chance, but as a result of an inaccuracy in the apparatus or its use by the person using it. This type of error tends to shift all the results in the same direction.
Zero error
A zero error is a type of systematic error caused by an instrument not being properly calibrated or adjusted. It then gives a non-zero value when the value should be zero.
Percentage uncertainty
Percentage uncertainty is the uncertainty divided by the measured value and expressed as a percentage.
Percentage difference
Percentage difference is the difference between two values divided by the mean and expressed as a percentage.
Scalar
A scalar quantity is one which has magnitude but not direction.
Vector
A vector quantity is one which has both magnitude and direction.
Vector triangle
A vector triangle is a type of scale diagram with two vectors drawn tip-to-tail, to show how they can be added together.
Resultant vector
The vector sum of two or more vectors.
The components of a vector
The components of a vector are the parts of a vector in two perpendicular directions.
One Newton
One Newton is the force needed to give a mass of 1 kg an acceleration of 1 metre per second squared.
Equilibrium
Objects are in equilibrium when all the forces acting on them in the same plane (coplanar forces) are balanced - there is zero net or resultant force.
The moment of a force
The moment of a force (or turning moment) is the product of the force and the perpendicular distance of its line of action from the pivot or axis.
The principle of moments
The principle of moments states that for an object to be in rotational equilibrium, the sum of the clockwise moments must equal the sum of the anti-clockwise moments.
Torque
Torque is the moment of a couple. The torque of a couple is the product of one of the forces and the perpendicular distance between them.
Centre of mass
The centre of mass of an object is the single point at which all of the mass of the object can be assumed to be situated.
Density
The density of an object is its mass per unit volume.
Archimedes’ principle
Archimedes’ principle states that the upward buoyant force (upthrust) exerted on an object immersed in a fluid is equal to the weight of the fluid displaced.
Work done
The work done, or energy transferred, is the product of the force and the distance moved by the force in the direction of movement.
A closed system.
A closed system is any system in which all the energy transfers are accounted for.
Energy or matter cannot enter or leave a closed system.
The principle of conservation of energy
The principle of conservation of energy states that the total energy of a closed system remains constant. Energy cannot be created or destroyed, it can only be transferred from one form to another.
Elasticity
Elasticity is the property of a body to resume its original shape or size once ethe deforming force or stress has been removed.
Hooke’s Law
Hooke’s Law states that the extension of an object is proprtional to the force that causes it, provided that the elastic limit is not exceeded.
Stress
Stress is force per unit cross-sectional area. It has unit Nm-2 or Pa and the symbol σ
Strain
Strain is extension per unit length. It has units and is therefore dimensionless.
Ductile
A ductile material can be drawn into wires and will show plastic deformation under tensile stress before breaking.
Malleable
A malleable material can be hammered or beaten into flat sheets and will show extensive plastic deformation when subject to compressive forces.
Brittle
A brittle material will break with little or no plastic deformation.
Hard
A hard material will resist plastic deformation by surface indentation or scratching.
Stiffness
Stiffness is the ability of a material to resist a tensile force.
Polymer
A polymer is a material made of long chains of molecules.
Ultimate tensile strength
Ultimate tensile strength is the maximum stress a material can withstsnad while being pulled or stretched, before it fails or breaks.
Young modulus
The Young modulus is the ratio of stress/strain for a given material.
Newton’s first law
A body will remain at rest or continue to move in a straight line at a constant velocity unless an external force acts on it.
Newton’s second law
The resultant force on an object is proportional to the rate of change of momentum of the object, and the momentum change takes place in the direction of the force.
Newton’s third law
If object A exerts a force on object B, then object B will exert an equal and opposite force on object A.
Impulse
Impulse is the product of force and the the time for which the force acts.
Elastic collision
An elastic collision is one in which both the momentum and kinetic energy are conserved. No energy is transferred to other forms.
Inelastic collision
An inelastic collision is one in which the momentum is conserved but some of the kinetic energy is transferred to other forms.
Electromotive force (e.m.f.)
The e.m.f. of a supply is the energy gained per unit charge by charges passing through the supply, when a form of energy is trasnferred to electrical energy carried by the charges. It is measure in volts or joules per coulomb.
Potential difference (p.d.)
The p.d. across a componenet is the energy transferred per unit charge by the charges passing through the component. It is measured in volts or joules per coulomb.
Ohm’s Law
Ohm’s law states that the current through a conductor is directly proportional to the potential difference across it, provided the temperature remains constant.
Kilowatt-hour
A kilowatt-hour is the energy transferred by 100 W in 3600 seconds. It si therefore equal to 3,600,000 J.
Kirchoff’s first law
Kirchoff’s first law states that the sum of currents entering a junction is equal to the sum of currents leaving the junction.
Kirchoff’s second law
Kirchoff’s second law states that in any close loop, the sum of the e.m.f. is equal to the sum of the products of the current and the resistance.
Potential divider
A potential divider circuit uses two resistors in series to split or divide the voltage of the supply in a chosen ratio so that a chosen voltage can be supplied to another device or circuit.
Terminal p.d.
The terminal p.d. is the p.d. recorded across the terminals of a cell. The difference between the e.m.f. and the p.d. when charge flows is called the ‘lost volts’.
Progressive wave
A progressive wave is a wave that tranfers energy away from a source.
Intensity
The intensity of a progressive wave is the rate at which energy is transferred perpendicular to the direction of wave travel.
I = P/A in Wm-2
Diffraction
Diffraction is the spreading out of a wave after passing around an obstacle or through a gap.
Interference
Interference is the addidtion of two or more waves (superposition) that causes a new wave pattern.
Plane polarisation
In a plane polarised wave the oscillations of the field and the direction of travel are confined to a single plane.
The principle of superposition
The principle of superposition states that when two or more waves of the same type meet, the resultant displacement of the wave can be found by adding the displacement of the individual waves.
Path difference
Path difference is the difference in distance (measured in m or numbers of wavelengths) travelled by two waves arriving at the same point.
Phase difference
Phase difference is the difference in phases, measured in radians, of two waves of the same frequency.
Nodes on a stationary wave
Nodes on a stationary wave are points at which there is no displacement of the particles at any time.
Anti-nodes on a stationary wave
Anti-nodes on a stationary wave are points where displacement is a maximum.
Quantum
A quantum is a small discrete unit of energy.
Photon
A photon is a quantum associated with electromagnetic radiation.
Electronvolt
The electronvolt is the kinetic energy gained by an electron when it is accelerated through a potential difference of 1 V.
Threshold frequency
The threshold frequency is the lowest frequency of radiation that will result in the emission of electrons from a particular metal surface.
Work function
The work function of a metal is the minimum energy that will result in the emission of an electron from a particular metal surface.
