Definitions - Topic 3 Electric Circuits - Edexcel

physics alevel

Conventional Current Flow

The flow of electric charge from positive to negative, used to describe the direction of current in a circuit.

Current

The rate of flow of charge in a circuit, measured in Amperes, represented by the symbol I.

Detecting Circuit

A circuit that contains a potential divider with a semiconductor that changes resistance with an external condition.

Diode

Components that allow current to pass through in one direction, and have a threshold voltage (typically 0.6 V).

Electromotive Force (EMF)

The energy supplied by a source per unit charge passing through it, measured in volts.

Electron Flow

The movement of electrons in a circuit from negative to positive.

Internal Resistance

The resistance within a power source that makes it harder for current to flow, causing energy dissipation.

Kirchoff’s First Law

The total current entering a junction is equal to the total current leaving it.

Kirchoff’s Second Law

The sum of EMF in any loop of the circuit is equal to the sum of the potential differences of each component.

Light Dependent Resistors (LDR)

Components whose resistance decreases as light intensity increases.

Ohmic Conductor

A conductor that follows Ohm's law, where current is directly proportional to potential difference, at constant temperature.

Ohm’s Law

Electric current is proportional to potential difference and inversely proportional to resistance.

Parallel Connection

A configuration where electrical components are on separate loops; potential difference is the same across each loop.

Potential Difference

The difference in electrical potential between two points, measured in volts.

Potential Divider

A setup of two or more resistors in series that splits potential difference based on their resistance.

Power

The rate of energy transfer in a circuit, calculated as the product of current and potential difference, measured in Watts.

Resistance

A measure of how difficult it is for current to flow in a circuit, measured in Ohms and represented by the symbol R.

Resistivity

A measure of how difficult it is for charge to move through a material, influenced by cross-sectional area, length, and resistance, measured in Ohm meters (⍴).

Semiconductors

Materials whose resistance varies based on external conditions.

Series Connection

Configuration where components are on the same loop; potential difference is divided among components depending on their resistance.

Superconductor

A material with zero resistivity below a critical temperature, used for efficient electricity transmission.

Terminal Potential Difference

The actual potential difference across the terminals of a power source, considering internal resistance.

Thermistor

Components that decrease resistance when heated; resistance decreases as temperature increases.

Variable Resistors

Resistors whose resistance can be adjusted, typically used with power supplies to change circuit voltage.

Voltmeter

A device for measuring potential difference between two points in a circuit, ideally with negligible resistance.

Valence band

Is the range of energy amounts that electrons in a solid have to keep them close to an atom.

The conduction band

Is the range of energy amounts that electrons in a solid have to become delocalised.

The energy of 1 electron

1.6×10^-13J

The energy of 1 mega electron volt

1.6×10^-19J

Drift Velocity

Is the overall velocity of charge carriers in a current.

The principle of charge conservation

The total electric charge in a closed system does not change

The principle of energy conservation

Energy cannot be created or destroyed, but transferred from one form to another.