AP Physics 2 key terms

The principle that the change in a system's internal energy equals the heat added to the system minus the work done by the system. It is a statement of energy conservation for thermal processes.

The total kinetic and potential energy of all particles in a system, depending only on its state variables such as temperature, pressure, and volume. It is a state function.

Energy transferred between a system and its surroundings due to a temperature difference. It is not a property of a system but a process of energy transfer.

Energy transferred when a force acts through a displacement, often expressed as pressure times change in volume for a gas. It is positive when the system expands.

A thermodynamic process in which the temperature of the system remains constant. For an ideal gas, the internal energy does not change, so heat added equals work done.

A process in which no heat is exchanged with the surroundings. Any work done changes the internal energy, often causing temperature changes in a gas.

A process that occurs at constant pressure. The work done by the system equals pressure times the change in volume, and heat capacity at constant pressure applies.

An equation of state for an ideal gas: pressure times volume equals number of moles times the universal gas constant times absolute temperature. It relates pressure, volume, and temperature.

A model that explains gas properties by treating particles as moving randomly and colliding elastically. It connects temperature to average molecular kinetic energy.

The amount of heat required to raise the temperature of one unit mass of a substance by one degree. It depends on the material and the phase.

The measurement of heat transfer in physical and chemical processes, often using the principle that heat lost by one object equals heat gained by another in an insulated system.

The law stating that the electric force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance between them.

A vector field that describes the force per unit positive charge at any point in space due to surrounding charges. It points in the direction of the force on a positive test charge.

The electric potential energy per unit positive charge at a point in an electric field. It is a scalar quantity measured in volts.

The energy a charged object possesses due to its position in an electric field. It equals the work done to bring the charge from infinity to that point.

Lines or surfaces on which the electric potential is the same everywhere. They are always perpendicular to electric field lines.

The ability of a system to store charge per unit potential difference. It is measured in farads and depends on the geometry and dielectric material.

A device that stores electric charge and energy in an electric field between two conductors separated by an insulator. Its capacitance is charge divided by voltage.

An insulating material placed between capacitor plates that increases capacitance by reducing the electric field for a given charge. It becomes polarized in an external field.

The relationship stating that the current through a conductor is directly proportional to the voltage across it, for a constant resistance. It is often written as voltage equals current times resistance.

A measure of how much a component opposes the flow of electric current, equal to voltage divided by current. It depends on material, length, and cross-sectional area.

The rate at which electric charge flows through a surface, measured in amperes. It is the amount of charge passing a point per unit time.

Two principles for circuit analysis: the junction rule states that current into a junction equals current out, and the loop rule states that the sum of voltage changes around a closed loop is zero.

A circuit in which components are connected end-to-end so the same current flows through each. The total resistance is the sum of individual resistances.

A circuit in which components are connected across the same voltage, so the current divides among branches. The total resistance is less than any individual resistance.

A vector field that exerts a force on moving charges and magnetic materials. It is produced by currents or permanent magnets and is measured in teslas.

The force exerted on a charge moving through a magnetic field, perpendicular to both the velocity and the field. Its magnitude is charge times speed times field times sine of the angle between velocity and field.

The production of an electric current or voltage in a conductor due to a changing magnetic field or motion through a magnetic field. It is described by Faraday's law.

A measure of the number of magnetic field lines passing through a given area, equal to field strength times area times cosine of the angle between field and area normal. It is measured in webers.

A principle stating that an induced current flows in a direction that opposes the change in magnetic flux that produced it. It reflects conservation of energy.

The bending of light or other waves when they pass from one medium to another due to a change in wave speed. It is described by Snell's law.

The ratio of the speed of light in a vacuum to its speed in a given medium. It determines how much light bends when entering the medium.

The relationship governing refraction: the product of the index of refraction and the sine of the angle of incidence equals the same product for the angle of refraction. It predicts how light bends at an interface.

The complete reflection of light at a boundary when it travels from a denser to a less dense medium at an angle greater than the critical angle. No light is refracted into the second medium.

A formula relating object distance, image distance, and focal length: one over object distance plus one over image distance equals one over focal length. It is used to locate images formed by thin lenses.

The superposition of two or more waves that results in a new wave pattern. Constructive interference occurs when waves are in phase, and destructive when out of phase.

The bending and spreading of waves when they pass through an opening or around an obstacle. It is most pronounced when the wavelength is comparable to the obstacle size.

An experiment where light passes through two narrow slits and forms an interference pattern of bright and dark fringes on a screen. It demonstrates the wave nature of light.

The emission of electrons from a material when light of sufficient frequency strikes it. It provides evidence that light behaves as particles called photons.

A quantum of electromagnetic radiation carrying energy proportional to its frequency. It has zero rest mass and travels at the speed of light.

The minimum energy required to remove an electron from the surface of a metal. It is a property of the material and appears in the photoelectric equation.