Glossary of Physical Terms

Physics: Glossary A Acceleration The change in velocity over time. Vector. Measured in m/s² Alpha Particle Two positive protons and two neutrons Alternating Current (A.C.) An electric current that reverses current periodically. This allows transformers and motors to work. Ammeter A device used for measuring current. Place in series to the circuit. Amplitude The maximum displacement a point in a wave moves from its resting point. Measured in metres Angle of Incidence The angle at which a wave hits a surface. Measured in degrees (。) Angle of Reflection The angle at which a wave reflects off a surface. Measured in degrees (。) Angle of Refraction The angle at which a wave is refracted after it has passed through a medium. Measured in degrees (。) B Bell A device that emits a loud noise by repeatedly hitting a metallic sheet that emits sound. Also tells you when class ends. Beta Particle A negative electron. Boyle’s Law Refers to gasses. Pressure and volume are inversely proportional. C Cell A mobile source of power, usually a battery. Charles’ Law The temperature of a gas is directly proportional to its volume. Chemical Energy The energy in a substance that has the potential to undergo a chemical reaction. Circuit A ring that allows electricity to travel through. Circuit Breaker A device that breaks a circuit if it detects a high-current. It does so by being attracted to the magnetic field that a high current produces. Compression To increase the pressure of a gas, increasing the density, or vice versa. Condensation A change of state where a gas cools into a liquid Conduction A method of heat transfer. When particles in a solid are heated, they vibrate more, encouraging nearby particles to vibrate more as well, thus “passing along” the heat. Conductor A material that allows a form of energy to pass through without much resistance. Constant Remaining the same Convection A method of heat transfer. When particles in a fluid are heated, they vibrate more, decreasing in density, so they rise above the dense colder air, which sinks. Convection Current When a heat source is placed on the bottom of a fluid, it heats the nearby air, causing it to rise, allowing the colder air to sink and be heated by the heat source, rise and repeat the process. Coulomb A unit of electrical charge. (C) Critical Angle The angle at which total internal reflection is achieved. Cross-sectional Area Refers to wires. The area of the cross section of the wire. Current The flow of electricity in a conductor. Represents the number of coulombs that pass a point in one second. Measured in Amps (A) D Density The mass of an object of a certain volume. Scalar. Measured in g/cm³ Direct Current (D.C.) A current that only travels in one direction. Distance The measurement between two points in space. Scalar. Measured in metres E Efficiency The percentage of total energy produced that goes to useful power. Electromagnet An electricity-powered magnet. Electromagnetic Wave A form of transverse wave that can travel in a vacuum at the speed of light. From shortest wavelength to longest: Radio, Micro, Infra-red, Visible, Ultra-violet, X, Gamma. Endothermic A phenomenon that absorbs heat energy. Energy The potential ability to do something. Scalar. Measured in Joules (J) Cannot be created or destroyed. Equilibrium A situation where two or more forces acting against each other have no resultant force. Evaporation A change in state where a liquid is changed into a gaseous. Exothermic A phenomenon that releases heat energy F Focal Length The distance between the centre of a lens and its focal point Focal Point The point at which a lens focuses light. Force A physical energy in a certain direction. Vector. Measured in Newtons (N). Formula A statement that states that one set of measurements is equal to another; an equation Frequency Number of times something occurs in a set time. Measured in Hertz (Hz) Fuse A device that breaks a circuit if it detects that the current is too high. It does so by overheating and melting if the current is too high. G Gas A state of matter that is characterized by its lack of bonds and its ability to take up space it is confined in. Gravity The force that pulls matter towards large bodies of mass. H Half-life The time it takes for half the mass of a material to fully decay. Hooke’s Law Refers to springs/flexibility. Force = constant ´ Extension Inertia The resistance of an object towards force Infra-red Radiation Radiation that is part of the infra-red spectrum. Associated with heat. Intermolecular Forces The bonds between molecules that hold the molecules in a certain position. Can be broken with enough energy. Insulator A material that resists allowing a form of energy to pass through. Joule A measure of energy. Joule’s Law Power is equal to Current times Potential. P=IV I J K Kelvin A measurement of temperature. 0。K is absolute zero and goes up in scale with the Celsius scale. Kinetic Energy The energy used to move in space. Measured in J. L Latent Heat Energy that is used in the transition between changing states in order to break intermolecular bonds to change state. Lens A shaped transparent material designed to refract light. Lens (Converging) Oval-shaped lens. Designed to focus light. Lens (Diverging) X-shaped lens. Designed to spread out light. Liquid A state of matter characterized by weakly bonded molecules and its ability to take the shape of its container. M Magnet A material that produces a dipole magnetic field (i.e. two poles) which affects other magnets Magnetic Susceptibility The degree of magnetization of a material in response to an applied magnetic field. Magnetic Retentivity The capacity for retaining magnetism after the action of the magnetizing force has ceased Mass The amount of particles in an object. Not to be confused with Weight. Measured in Kilograms (Kg) Molecule A particle made up of atoms. Motor An electric-powered rotational motion device. N Newtons A measurement of force in a certain direction. Scalar. (N) O Oscillation Vibration. To move back and forth in a repetitive fashion. P Parallel Circuit A circuit that has branching paths that still make a complete circuit. Power The energy consumed over a certain time. Scalar. Measured in J/s or Watts (W) Potential (Electricity) The amount of Joules per Coulomb there is at a point in a circuit. Measured in Volts (V) Potential Difference The difference in potential between two points in a circuit. Represents how many Joules there are in one Coulomb. Measured in Volts (V) Potential Energy The energy that an object has that is not in use/in storage. E.g. Gravitational potential energy. Pressure Force applied to a certain area. Measured in N/m² or Pascals (Pa) Q R Radiation A method of heat transfer that does not require a medium to travel through. It travels as an electromagnetic wave. Radioactive Decay Unstable nuclei will lose its mass by giving off alpha and beta particles and gamma rays. Rarefaction A part of a longitudinal wave that has less density than its density at rest. Reflection The throwing back of a wave by a surface without absorbing it. Refraction The distortion of a wave as it passes from one medium through another. Relay A magnet-activated switch. Renewable Energy Energy that can be reused over and over. E.g. wind, solar. Resistance The measure of how difficult it is for electricity to travel though the circuit. Measured in Ohms (Ω) Scalar A measurement that has magnitude (size) but no direction e.g. temperature Series Circuit A circuit where all the elements are along the same line with no branching paths. Solenoid A wrapped coil of wire. Solid A state of matter characterized by molecules that have strong bonds, and do not change shape on its own. Specific Heat Capacity The amount of thermal energy needed to increase the temperature of 1 gram of a substance by 1。K. Also known as Thermal Capacity Speed The distance travelled in a certain amount of time. Scalar. Measured in m/s S Surface Area The area of the surface of an object. Static Electricity A material that has a deficiency of electrons is attracted to another material that has an abundance of electrons. T Temperature The collective intensity of the vibration of particles in an object. Thermal Capacity The amount of thermal energy needed to increase the temperature of 1 gram of a substance by 1。K. Also known as Specific Heat Capacity Time A measure of distance traveled in the dimension of time. If you really need a definition of time, godspeed to you. Measured in seconds (s). Total Internal Reflection When the angle of refraction is more than 90。, the wave bounces off the surface as if it were a reflective surface. Transformer A device that uses the magnetic field created by an alternating current to change the voltage and current intensity. Step-up transformers increase voltage but decrease current. Step-down transformers increase current but decrease voltage. U Unit An arbitrary measurement of some kind. (e.g. one unit of time, one unit of volume) V Vector A measurement that has magnitude (size) and direction e.g. acceleration Velocity Distance displaced in a certain direction in a certain time. Vector. Measured in m/s Virtual What appears to be real is, in actuality, not. Voltmeter An instrument used to measure Potential Difference. Put in parallel to the element which you want to measure Volume The measurement of 3D space. Scalar. Measured in m³ W Wave A transfer of energy through vibrations. Wave A type of wave that vibrates in parallel to the direction of the wave. (Longitudinal) Wave (Transverse) A type of wave that vibrates perpendicular to the direction of the wave. Wavelength The distance over which a wave repeats. Measured in metres Weight The gravitational pull of an object towards the earth. Not to be confused with Mass. Measured in Newtons. Work The total amount of energy needed to complete a task.