GCSE Physics: Current Electricity

Vocabulary flashcards covering current, charge, potential difference, resistance, circuit rules, component behaviors, and I-V characteristics from GCSE Physics Current Electricity lessons 1 to 6.

Electric Current

The rate of flow of electrical charge in a circuit.

Coulomb ($\text{C}$)

The standard unit of measurement for electrical charge.

Ampere ($\text{A}$)

The unit of measurement for electric current, where $1\,\text{A} = 1\,\text{C/s}$ ($1\text{ coulomb per second}$).

Charge Flow Equation

$Q = It$, where $Q$ is charge flow in coulombs ($\text{C}$), $I$ is current in amperes ($\text{A}$), and $t$ is time in seconds ($\text{s}$).

Potential Difference ($V$)

The energy transferred or work done per coulomb of charge ($V = \frac{E}{Q}$), measured in volts ($\text{V}$).

Volt ($\text{V}$)

The unit of measurement for potential difference (or voltage), equivalent to joules per coulomb ($\text{J/C}$).

Voltmeter

An instrument used to measure potential difference in a circuit, which must always be connected in parallel across a component.

Ammeter

An instrument used to measure electric current flowing through a circuit, which is placed in series.

Electrical Resistance ($R$)

The ratio of potential difference across an electrical component to the current flowing through it ($R = \frac{V}{I}$).

Ohm ($\Omega$)

The unit of electrical resistance, represented by the Greek letter omega ($\Omega$).

Ohmic Conductor

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

Filament Lamp

A component whose resistance increases as current and temperature increase, caused by increased vibrations of metal ions colliding with flowing electrons.

Diode

A component that allows current to flow in only one direction (forward bias) above a threshold potential difference of approximately $0.6\,\text{V}$, with very high or infinite resistance in reverse bias.

Light Emitting Diode (LED)

A diode that allows current to flow in one direction only and emits light when current passes through it.

Thermistor

A temperature-dependent resistor whose resistance decreases as temperature increases; commonly used in thermostats.

Light Dependent Resistor (LDR)

A resistor whose resistance decreases as light intensity increases; commonly used to switch lights on automatically when it gets dark.

Fuse

A safety component that melts or 'blows' to break the circuit if too much current flows through it.

Series Circuit Current Rule

The current has the exact same value at all points in a single closed loop ($I_1 = I_2 = I_3$).

Series Circuit Potential Difference Rule

The total potential difference of the power supply is shared between the components ($V_{\text{supply}} = V_1 + V_2 + \dots$), split in the same ratio as their resistances ($V_X : V_Y = R_X : R_Y$).

Series Circuit Total Resistance Rule

The total resistance is the sum of the resistances of each individual component ($R_{\text{total}} = R_1 + R_2 + \dots + R_n$).

Parallel Circuit Potential Difference Rule

The potential difference across each separate branch or component in parallel is identical ($V_{\text{supply}} = V_1 = V_2 = \dots$).

Parallel Circuit Current Rule

The total current through the whole circuit is equal to the sum of the currents flowing through the separate branches ($I_{\text{total}} = I_1 + I_2 + \dots$).

Parallel Circuit Total Resistance Rule

Adding resistors in parallel provides additional branches for charge to flow at the same potential difference, increasing total current and making total resistance less than the smallest individual resistor.

Resistance vs. Length Relationship (RP3)

The resistance of a wire is directly proportional to its length ($R \propto L$) at constant temperature, producing a straight line through the origin on a graph.

Electric Current

The rate at which electric charge flows past a given point in an electrical circuit, determined by the net movement of charge carriers.

Delocalised Electrons in Conduction

Negatively charged subatomic particles that are free to drift between stationary, positively charged metal ions to transfer charge and energy through a metallic conductor.

Coulomb ($\text{C}$)

The standard SI unit of electrical charge, equivalent to the quantity of electricity conveyed by a steady electric current of one ampere flowing for one second.

Ampere ($\text{A}$)

The SI base unit of electric current, defined as a rate of charge flow equivalent to one coulomb per second ($1\,\text{A} = 1\,\text{C/s}$).

Charge Flow Equation

$Q = It$, where $Q$ represents charge flow in coulombs ($\text{C}$), $I$ represents current in amperes ($\text{A}$), and $t$ represents the time elapsed in seconds ($\text{s}$).

Potential Difference ($V$)

The amount of energy transferred or work done per coulomb of electrical charge passing between two points in a circuit ($V = \frac{E}{Q}$).

Volt ($\text{V}$)

The SI unit of potential difference or electromotive force, defined as an energy transfer of one joule per coulomb of charge ($1\,\text{V} = 1\,\text{J/C}$).

Energy Transferred by Charge Equation

$E = QV$, where $E$ is work done or energy transferred in joules ($\text{J}$), $Q$ is electrical charge in coulombs ($\text{C}$), and $V$ is potential difference in volts ($\text{V}$).

Voltmeter

A high-resistance measuring instrument that must be connected in parallel across an electrical component to measure the potential difference across it.

Ammeter

A low-resistance measuring device placed in series within a circuit loop to measure the electric current flowing directly through that point.

Electrical Resistance ($R$)

A quantitative measure of the opposition a material or component presents to the flow of electric current, defined as the ratio of potential difference across it to the current passing through it ($R = \frac{V}{I}$).

Ohm ($\Omega$)

The standard unit of electrical resistance, equal to the resistance across a conductor when a potential difference of one volt produces a current of one ampere ($1\,\Omega = 1\,\text{V/A}$).

Ohm's Law Equation

$V = IR$, relating potential difference in volts ($\text{V}$), electric current in amperes ($\text{A}$), and electrical resistance in ohms ($\Omega$).

Ohmic Conductor

An electrical conductor for which current is directly proportional to potential difference at a constant temperature, resulting in a constant electrical resistance and a linear graph through the origin.

Filament Lamp I-V Characteristic

A non-linear, S-shaped current-voltage graph where the curve levels off at higher voltages because the electrical resistance increases as the current and filament temperature rise.

Cause of Filament Lamp Resistance Increase

As electrical current increases, the metal filament heats up, causing positive metal ions to vibrate more vigorously and increase collisions with flowing electrons.

Semiconductor Diode

A non-linear component that conducts electric current easily in forward bias but presents extremely high or virtually infinite resistance in reverse bias.

Diode Forward Bias Threshold

The minimum forward potential difference (approximately $0.6\,\text{V}$) required across a semiconductor diode before significant current begins to flow through it.

Light Emitting Diode (LED)

A specialized diode that permits current flow in one direction only and efficiently emits visible light when an electric current passes through it in forward bias.

Thermistor

A temperature-dependent semiconductor resistor whose electrical resistance decreases significantly as its temperature increases.

Practical Thermistor Application

Used in thermostats, digital thermometers, and central heating systems to monitor temperature changes and regulate electrical output.

Light Dependent Resistor (LDR)

A photosensitive semiconductor component whose electrical resistance decreases substantially as the incident light intensity increases.

Practical LDR Application

Used in automated streetlights, security lighting, and camera light meters to detect changes in ambient light levels and activate circuits when darkness falls.

Variable Resistor (Rheostat)

A circuit component whose electrical resistance can be manually varied to adjust the overall current flowing through a circuit or alter the potential difference across other components.

Electric Fuse

A safety device containing a thin wire designed to heat up and melt ('blow') when current exceeds a predetermined threshold, permanently severing the circuit to prevent fire or damage.

Cell vs. Battery

A single chemical unit that produces an electrical potential difference, whereas a battery consists of two or more interconnected cells joined together in series.

Series Circuit Current Rule

Electric current is identical and constant at every position within a single closed circuit loop ($I_1 = I_2 = I_3$), as there is only one pathway for charge flow.

Series Circuit Potential Difference Rule

The total potential difference supplied by the power source is shared among all components connected in series ($V_{\text{supply}} = V_1 + V_2 + \dots + V_n$).

Series Potential Divider Ratio

The supply voltage in a series arrangement is distributed across components in direct proportion to their individual resistances ($V_X : V_Y = R_X : R_Y$).

Series Circuit Total Resistance Rule

The total equivalent resistance of components in series is the algebraic sum of their separate individual resistances ($R_{\text{total}} = R_1 + R_2 + \dots + R_n$).

Parallel Circuit Potential Difference Rule

The full potential difference supplied by the power source is applied identically across each independent branch in a parallel circuit ($V_{\text{supply}} = V_1 = V_2 = \dots$).

Parallel Circuit Current Rule

The total electric current delivered from the power supply is equal to the sum of the currents flowing through each parallel branch ($I_{\text{total}} = I_1 + I_2 + \dots + I_n$).

Parallel Circuit Total Resistance Rule

Connecting resistors in parallel reduces total resistance such that the effective combined resistance is strictly less than the resistance of the smallest individual resistor.

Mechanism of Reduced Resistance in Parallel

Adding parallel branches introduces extra independent pathways for charge to flow at the same potential difference, increasing total circuit current and lowering overall resistance.

Resistance vs. Wire Length Relationship (RP3)

The electrical resistance of a uniform metal wire is directly proportional to its length ($R \propto L$) at constant temperature, producing a straight line passing through the origin on an R-L graph.

Component I-V Characteristics Method (RP4)

An experimental setup using an ammeter in series, a voltmeter across the test component, and a variable resistor to systematically vary and record current and potential difference.