Physics 30 Diploma key terms

A vector quantity found by multiplying an object's mass by its velocity. It measures how hard it is to stop the object and is conserved in isolated systems.

The product of an average force and the time over which it acts. It equals the change in momentum, so a longer contact time reduces the force needed.

In a closed system with no external net force, the total momentum before an interaction equals the total momentum after it, whether the collision is elastic or inelastic.

A collision in which both momentum and kinetic energy are conserved. Objects bounce apart with no loss of kinetic energy to heat, sound, or deformation.

A collision in which momentum is conserved but kinetic energy is not. Some kinetic energy converts to heat, sound, or deformation, and objects may stick together.

A region around a charge where another charge experiences a force. Its strength equals the force per unit positive charge, and field lines point away from positive charges.

The electrostatic force between two point charges is proportional to the product of the charges and inversely proportional to the square of the distance between them, acting along the line joining them.

The work done per unit positive charge moving between two points in a circuit or field. Measured in volts, it drives current through a conductor.

The rate at which electric charge flows past a point in a circuit, measured in amperes. One ampere equals one coulomb of charge passing each second.

The opposition a material offers to current flow, measured in ohms. It equals the potential difference across a component divided by the current through it.

For a conductor at constant temperature, the potential difference across it is directly proportional to the current through it, with resistance as the constant of proportionality.

The smallest known free charge magnitude, about 1.60 times ten to the negative nineteen coulombs. Protons and electrons carry this charge, opposite in sign.

The principle that any observable charge is an integer multiple of the elementary charge, because charge comes in discrete units carried by particles such as electrons and protons.

An experiment balancing electric and gravitational forces on tiny charged oil droplets, allowing measurement of the elementary charge and demonstrating that charge is quantized.

A vector field around magnets and moving charges that exerts forces on other moving charges and magnetic materials. Its direction is given by the north pole of a compass needle.

The force on a charge moving through a magnetic field, perpendicular to both the velocity and the field. Its magnitude depends on charge, speed, field strength, and angle.

A convention for finding directions of magnetic forces and induced fields: point fingers along velocity, curl toward the field, and the thumb gives the force on a positive charge.

The production of an electric potential difference in a conductor by a changing magnetic flux through it, the principle behind generators and transformers.

A measure of the number of magnetic field lines passing through a given area, equal to field strength times area times the cosine of the angle between them.

An induced current flows in a direction whose own magnetic field opposes the change in flux that produced it, reflecting conservation of energy.

A discrete packet of electromagnetic energy whose energy equals Planck's constant times frequency. Light behaves as both a wave and a stream of these particles.

The emission of electrons from a metal surface when light of sufficiently high frequency strikes it, providing evidence that light energy is quantized.

The minimum energy needed to remove an electron from the surface of a particular metal. Light below the corresponding threshold frequency ejects no electrons.

A fundamental constant linking a photon's energy to its frequency, approximately 6.63 times ten to the negative thirty-four joule seconds. It sets the scale of quantum effects.

The minimum light frequency that can eject electrons from a given metal surface. Below this value, no electrons are emitted regardless of light intensity.

The wavelength associated with a moving particle, equal to Planck's constant divided by its momentum. It explains electron diffraction and wave behaviour of matter.

The principle that light and matter exhibit both wave and particle properties depending on the experiment, such as interference versus photoelectric emission.

The pattern of specific wavelengths emitted or absorbed by an element when its electrons change energy levels, appearing as discrete lines rather than a continuous band.

A discrete allowed energy state for an electron in an atom. Transitions between levels absorb or emit photons with energy equal to the difference.

Radiation carrying enough energy to remove electrons from atoms, including alpha particles, beta particles, gamma rays, and high-energy photons. It can damage living tissue.

Radioactive decay in which a nucleus emits an alpha particle, two protons and two neutrons, decreasing its mass number by four and atomic number by two.

Radioactive decay in which a neutron converts to a proton, emitting a beta particle and an antineutrino. The atomic number rises by one while mass number stays the same.

The emission of a high-energy photon from an excited nucleus as it drops to a lower energy state, without changing the mass number or atomic number.

The time required for half the nuclei in a radioactive sample to decay. After each half-life the remaining undecayed amount halves again.

The difference between the mass of a nucleus and the sum of its separate nucleon masses. It appears as binding energy according to mass-energy equivalence.

The energy required to separate a nucleus completely into its individual protons and neutrons. It equals the mass defect multiplied by the square of the speed of light.

The relationship stating that mass and energy are interchangeable, with energy equal to mass times the square of the speed of light. It underlies nuclear energy calculations.

The splitting of a heavy nucleus into lighter nuclei, releasing energy and usually neutrons. It powers nuclear reactors and can sustain a chain reaction.

The joining of light nuclei into a heavier one, releasing energy because the product is more tightly bound. It powers stars and requires extremely high temperatures.