Physics Keywords Flashcards
Oscillate
To move to and fro about a certain position along a line (vibrate).
Angle of incidence
The angle between the incidence (incoming) ray and the normal.
Beta radiation
Beta particles, high energy electrons created in, and emitted from unstable nuclei.
Boiling point
The temperature at which a pure substances boils or condenses.
Split-ring communicator
Metal contacts on the coil of a direct current motor that connects the rotating coil continuously to its electrical power supply.
Alpha radiation
Alpha particles, each containing two protons and two neutrons, emitted by unstable nuclei. Also referred to as a helium nucleus.
Ohm’s law
The current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor.
Momentum
This equals mass (in kg) x velocity (in m/s).
Transmission
A wave passing through a substance.
Thermal conductivity
The property of a material that determines the energy transfer through it by conduction.
Internal energy
The energy of the particles within a substance due to their individual motion and positions.
Nuclear fusion
The process where small nuclei are fused together to form a larger nucleus.
Magnification
The image height ÷ the object height
Magnetic field line
Line in a magnetic field along which a magnetic compass points - also called a line of force.
Specific latent heat of fusion
The energy needed to melt 1 kg of a substance with no change of temperature.
Errors
In readings, measurements or results. Also known as uncertainties.
Work
The energy transferred by a force. Work done (Joules, J) = force (Newtons, N) x distance moved in the direction of the force (metres, m)
Weight
The force of gravity on an object (in Newtons, N).
Compression
Squeezing or pressing together.
White light
Light that includes all the colours of the visible spectrum.
Red giant
A star that has expanded and cooled (due to expending its hydrogen fuel and begins fusing helium nuclei), resulting in it becoming red and much larger and cooler than it was before it expanded.
Longitudinal waves
Waves in which the vibrations are parallel to the direction of energy transfer. The wave direction is the same as the oscillations.
Step-up transformer
An electrical device that is used to step-up (increase) the size of an alternating potential difference.
Parallel (circuit)
Components connected in a circuit so that the potential difference across each is the same.
Alternating current (A.C.)
An electrical current in a circuit that repeatedly reverses its direction.
Gamma radiation
Electromagnetic radiation emitted from unstable nuclei in radioactive substances.
Infra-red radiation
Electromagnetic waves between visible light and microwaves in the electromagnetic spectrum.
Driving force
The force of a vehicle that makes it move (also called motive force or thrust).
Induced magnetism
Magnetisation of an unmagnetised magnetic material by placing it in a magnetic field.
Generator effect
The production of a potential difference using a magnetic field.
Inverse proportionality
This is where two variables are related such that making one variable n times bigger, causes the other to become n times smaller (e.g. doubling one quantity causes the other to halve).
Risk
The likelihood that a hazard will actually cause harm.
S-wave Secondary seismic wave
Transverse waves that shake the Earth from side to side as they pass through.
Count rate
The number of counts per second detected by a Geiger counter.
Inertia
The tendency of an object to stay at rest or to continue in a uniform motion.
Latent heat
The energy transferred to or from a substance when it changes its state.
Angle of reflection
The angle between the reflected (outgoing) ray and the normal.
Atomic number
The number of protons (which equals the number of electrons) in an atom. Also called the proton number.
Scalar
A physical quantity, such as mass or energy, that has a magnitude only (unlike a vector which has magnitude and direction).
Concave (diverging) lens
A lens that makes parallel rays diverge (spread out).
Newton’s third law of motion
When two objects interact with each other, they exert equal and opposite forces on each other.
Effort
The force applied to a device, used to raise a weight or move an object.
Nuclear fission
The process in which certain, large nuclei (uranium-235 and plutonium-239) are spilt into two fragments, releasing energy and two or three more neutrons as a result.
Protostar
The concentration of dust clouds and gas in space that forms a star.
Reflection
The change of direction of a light ray or wave at a boundary when the ray or wave stays in the incident medium.
Renewable energy
Energy from natural sources that is always being replenished so that it will never run out.
Dissipation of energy
The energy that is not usefully transferred or stored. Transferred to less useful forms e.g. thermal energy.
Earth wire
The wire in a mains cable used to connect the metal case of an appliance to earth.
Supernova
The explosion of a massive star after fusion in its core ceases and the matter surrounding its core collapses on to the core and rebounds.
Limit of proportionality
The limit for Hooke’s law applied to the extension of a stretched spring.
Redshift
The increase in the wavelength of electromagnetic waves emitted by a star or galaxy due to its motion away from us. The faster the speed of the star or galaxy, the greater the redshift is.
Neutrons
Uncharged particles of the same mass as protons. The nucleus of an atom consists of protons and neutrons.
Series (circuit)
Components connected in a circuit in such a way that the same current passes through each of them.
Hooke’s law
The extension of a spring is directly proportional to the force applied, as long as its limit of proportionality is not exceeded.
Extension
The increase in length of a spring (or material) from its original length.
Motor effect
When a current is passed along a wire in a magnetic field, and the wire is not parallel to the lines of the magnetic field, a force is exerted on the wire by the magnetic field.
Red supergiant
A star much more massive than our Sun that has expanded and cooled (due to expending its hydrogen fuel and begins fusing helium nuclei), resulting in it becoming red and much larger and cooler than it was before it expanded.
Directly proportional
A graph will show direct proportionality if the line of best fit is a straight line and passes through the origin.
Specular reflection
Reflection from a smooth surface. Each light ray is reflected in a single direction.
White dwarf
A star that has collapsed from the red giant stage to become much smaller, hotter, and denser.
P-wave (Primary seismic wave)
Longitudinal waves that push or pull on the material that they move through, as they move through the Earth.
Principle of moments
For an object in equilibrium, the sum of all the clockwise moments about any point = the sum of all the anti-clockwise moments about that same point.
Diode
A non-ohmic conductor that has a much higher resistance in one direction (its reverse direction) than in the other direction (its forward direction).
Plugs
A plug has an insulated case and is used to connect the cable from an appliance to a socket.
National grid
The network of cables and transformers used to transfer electricity from power stations to consumers (I.e. homes, shops, offices, factories, etc.).
Physical change
A change in which no new substances are produced.
Ionisation
Any process which causes atoms to become charged.
LED (Light emitting diode)
A diode that emits light when it conducts.
Closed system
An object or group of objects for which the total energy is constant.
Resultant force
A single force that has the same effect as all the forces acting on the object.
Parallelogram of forms
A geometrical method used to find the resultant of two forces that do not act along the same line.
Rarefaction
Stretched apart.
Velocity
Speed in a given direction (in metres per second, m/s).
LDR (Light dependent resistor)
A resistor whose resistance depends on the intensity of the light it is exposed to.
Thermistor
A resistor whose resistance depends on the temperature of the thermistor.
CMBR (Cosmic Microwave Background Radiation)
Electromagnetic radiation that has been travelling through space ever since it was created shortly after the Big Bang.
Wavelength
The distance from one wave crest to the next (metres, m).
Terminal velocity
The velocity reached by an object when the drag force on it is equal and opposite to the force making it move. e.g. Air resistance and gravity.
Force multiplier
A lever used so that a weight or force can be moved by a smaller force.
Refraction
The change of direction of a light ray when it passes across a boundary between two transparent substances (including air).