GCSE Physics: Energy, Electricity, Particle Model, and Atomic Structure

Comprehensive vocabulary flashcards covering key definitions, equations, circuit components, and concepts from GCSE Physics.

System

An object or group of objects in which energy changes can occur.

Kinetic Energy

The energy of a moving object, calculated using the equation $E_k = 0.5 \times m \times v^2$, where $E_k$ is kinetic energy in joules ($\text{J}$), $m$ is mass in kilograms ($\text{kg}$), and $v$ is speed in metres per second ($\text{m/s}$).

Elastic Potential Energy

The energy stored in a stretched spring, calculated as $E_e = 0.5 \times k \times e^2$, where $k$ is the spring constant in newtons per metre ($\text{N/m}$) and $e$ is extension in metres ($\text{m}$), assuming the limit of proportionality has not been exceeded.

Gravitational Potential Energy (g.p.e.)

The energy gained by an object raised above ground level, calculated using $E_p = m \times g \times h$, where $m$ is mass in kilograms ($\text{kg}$), $g$ is gravitational field strength in newtons per kilogram ($\text{N/kg}$), and $h$ is height in metres ($\text{m}$).

Specific Heat Capacity

The amount of energy required to raise the temperature of one kilogram of a substance by one degree Celsius, calculated from $\Delta E = m \times c \times \Delta\theta$.

Power

The rate at which energy is transferred or the rate at which work is done, calculated by $P = \frac{E}{t}$ or $P = \frac{W}{t}$.

Watt ($\text{W}$)

The unit of power, where an energy transfer of $1\text{ joule per second}$ is equal to a power of $1\text{ watt}$.

Law of Conservation of Energy

A fundamental principle stating that energy can be transferred usefully, stored, or dissipated, but cannot be created or destroyed.

Dissipated Energy

Energy that spreads out into less useful forms during system changes, often described as being 'wasted'.

Thermal Conductivity

A property of a material measuring how well it conducts heat; the higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across it.

Energy Efficiency

The ratio of useful output to total input, calculated either as $\text{efficiency} = \frac{\text{useful output energy transfer}}{\text{total input energy transfer}}$ or $\text{efficiency} = \frac{\text{useful power output}}{\text{total power input}}$.

Renewable Energy Resource

An energy resource that is being (or can be) replenished as it is used, such as wind, solar, or hydro-electricity.

Electric Current

A flow of electrical charge, with the size of the current being the rate of flow of electrical charge ($Q = I \times t$).

Potential Difference (pd)

The energy transfer per unit charge between two points in a circuit; for charge to flow in a closed circuit, there must be a source of potential difference.

Electrical Resistance

The measure of a component's opposition to current flow, calculated using $V = I \times R$, where $V$ is potential difference in volts ($\text{V}$), $I$ is current in amperes ($\text{A}$), and $R$ is resistance in ohms ($\Omega$).

Ohmic Conductor

A conductor for which the current is directly proportional to the potential difference across it at constant temperature, meaning resistance remains constant as current changes.

Current–Potential Difference Graph (Ohmic Conductor)

A straight-line graph passing through the origin, demonstrating that current is directly proportional to potential difference.

Current–Potential Difference Graph (Filament Lamp)

An S-shaped characteristic curve showing that as current increases, filament temperature rises, increasing resistance and shallowing the curve at higher voltages.

Current–Potential Difference Graph (Diode)

A characteristic curve showing zero current in reverse bias due to very high resistance, and current increasing sharply once forward threshold voltage is reached.

Thermistor

A temperature-sensitive resistor whose electrical resistance decreases as its temperature increases.

Light Dependent Resistor (LDR)

A light-sensitive resistor whose electrical resistance decreases as the light intensity on it increases.

Series Circuit Resistance Rule

In a series circuit, the total resistance of two components is the sum of their individual resistances: $R_{\text{total}} = R_1 + R_2$.

Parallel Circuit Resistance Rule

In a parallel circuit, the total resistance of two resistors joined in parallel is less than the resistance of the smallest individual resistor.

UK Mains Electricity

An alternating current ($\text{ac}$) domestic electricity supply with a frequency of $50\text{ Hz}$ and a potential difference of about $230\text{ V}$.

Live Wire

The brown wire in a three-core mains cable that carries the alternating potential difference from the supply at about $230\text{ V}$.

Neutral Wire

The blue wire in a three-core mains cable that completes the circuit, held at or close to earth potential ($0\text{ V}$).

Earth Wire

The green-and-yellow-striped safety wire held at $0\text{ V}$ that stops the appliance from becoming live and only carries current if there is a fault.

Electrical Power in Circuits

The power transferred in a circuit device, calculated using $P = V \times I$ or $P = I^2 \times R$, where $P$ is power in watts ($\text{W}$).

The National Grid

A system of cables and transformers linking power stations across the country to consumers.

Step-up Transformer

A transformer used in the National Grid to increase the potential difference from the power station to transmission cables, reducing energy losses.

Step-down Transformer

A transformer used in the National Grid to decrease the potential difference from transmission cables to a lower, safer value for domestic use.

Density

The mass per unit volume of a substance, defined by $\rho = \frac{m}{V}$, where $\rho$ is density in kilograms per metre cubed ($\text{kg/m}^3$), $m$ is mass in kilograms ($\text{kg}$), and $V$ is volume in metres cubed ($\text{m}^3$).

Internal Energy

The total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.

Specific Latent Heat

The amount of energy required to change the state of one kilogram of a substance with no change in temperature, calculated using $E = m \times L$.

Specific Latent Heat of Fusion

The energy required per kilogram to change a substance from solid to liquid without changing its temperature.

Specific Latent Heat of Vaporisation

The energy required per kilogram to change a substance from liquid to vapour without changing its temperature.

Atomic Number

The number of protons in the nucleus of an atom of a specific chemical element.

Mass Number

The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Plum Pudding Model

An early atomic model proposing that an atom is a uniform sphere of positive charge with negatively charged electrons embedded within it.

Nuclear Model

The model established after the alpha particle scattering experiment, concluding that an atom's mass and positive charge are concentrated in a tiny central nucleus.

Radioactive Decay

A random nuclear process in which an unstable atomic nucleus emits nuclear radiation to become more stable.

Activity

The rate at which a source of unstable nuclei decays, measured in becquerels ($\text{Bq}$).

Count-rate

The number of radioactive decays recorded each second by a radiation detector, such as a Geiger-Muller tube.

Alpha Particle ($\alpha$)

Nuclear radiation consisting of two neutrons and two protons (identical to a helium-4 nucleus, $^4_2\text{He}$), causing mass to decrease by $4$ and atomic number to decrease by $2$ upon emission.

Beta Particle ($\beta$)

A high-speed electron ($^0_{-1}\text{e}$) ejected from the nucleus when a neutron turns into a proton, leaving the mass number unchanged while increasing atomic number by $1$.

Gamma Ray ($\gamma$)

High-frequency electromagnetic radiation emitted from the nucleus that causes no change in the mass or charge of the nucleus.

Half-life

The time it takes for the number of nuclei of a radioactive isotope in a sample to halve, or for the count rate (or activity) to fall to half its initial level.

Radioactive Contamination

The unwanted presence of materials containing radioactive atoms on or inside other materials.

Irradiation

The process of exposing an object to nuclear radiation; the irradiated object does not become radioactive.