AQA Physics 8463 Electricity Vocabulary Flashcards

Vocabulary flashcards reviewing AQA Physics 8463 Electricity concepts, equations, mains safety, and required practicals.

Electric current

The rate of flow of electrical charge.

Condition for charge flow

A closed circuit containing a source of potential difference.

Charge flow equation

$Q = I \times t$, linking charge flow ($Q$), current ($I$), and time ($t$).

Coulomb ($C$)

The unit of charge flow.

Ampere ($A$)

The unit of current.

Unit of time in $Q = I \times t$

Seconds ($s$).

Current in a single closed loop

Has the same value at every point.

Potential difference

A measure of the energy transferred per unit charge between two points.

AQA term for voltage

Potential difference, although correct use of voltage also gains credit.

Resistance

A measure of how difficult it is for current to flow through a component.

Equation linking potential difference, current, and resistance

$V = I \times R$.

Ohm ($\Omega$)

The unit of resistance.

Effect of resistance on current

For a fixed potential difference, current decreases as resistance increases.

Ammeter connection

Connected in series with the component.

Ammeter

An instrument used to measure current.

Voltmeter connection

Connected in parallel across the component.

Voltmeter

An instrument used to measure potential difference across a component.

Ohmic conductor

A conductor whose current is directly proportional to potential difference when its temperature is constant.

Resistance of an ohmic conductor

Remains constant as current changes, provided the temperature is constant.

I-V graph for an ohmic conductor

A straight line through the origin.

Filament lamp resistance increase

Occurs because the filament gets hotter as current increases, increasing its resistance.

I-V graph for a filament lamp

Shows a curved relationship because resistance increases as the filament temperature rises.

Diode current flow

Flows mainly in one direction only.

Reverse direction resistance of a diode

Very high.

Thermistor resistance behavior

Resistance decreases as temperature increases.

Application of a thermistor

A thermostat or temperature-sensing circuit.

LDR resistance behavior

Resistance decreases as light intensity increases.

Application of an LDR

Automatic lights that switch on when it becomes dark.

Experimental measurement of resistance

Measure current through a component and potential difference across it, then calculate $R = \frac{V}{I}$.

Required Practical 3

Investigates factors affecting resistance: the length of a wire at constant temperature and combinations of resistors in series and parallel.

Wire length and resistance relationship

As the length of a wire increases, its resistance increases.

Temperature control in resistance experiments

Wire temperature should be kept as constant as possible because resistance can change with temperature.

Required Practical 4

Investigates the I-V characteristics of a resistor at constant temperature, a filament lamp, and a diode.

I-V characteristic

The relationship between current through a component and potential difference across it.

Purpose of repeat readings in I-V practical

Improves reliability and helps identify anomalous results.

Basic circuit connection methods

Series and parallel.

Current in a series circuit

The same current flows through every component.

Potential difference in a series circuit

The supply potential difference is shared between the components.

Total resistance in a series circuit

$$R_{\text{total}} = R_1 + R_2 + \dots$$

Adding a resistor in series

Increases the total resistance of the circuit.

Potential difference in a parallel circuit

The potential difference across each branch is the same.

Current at a junction in a parallel circuit

The total current equals the sum of the currents in the separate branches.

Total resistance of resistors in parallel

Less than the resistance of the smallest individual resistor.

AQA parallel resistance calculation requirement

AQA does not require calculation of the total resistance of two resistors in parallel.

Reason parallel resistors reduce total resistance

Adding resistors in parallel provides additional paths for charge, allowing a greater total current to flow for the same potential difference.

Direct potential difference

A potential difference that acts in one direction only.

Alternating potential difference

A potential difference that repeatedly changes direction.

UK mains electricity supply type

Alternating current (ac).

Frequency of UK domestic mains supply

$50\,\text{Hz}$.

Potential difference of UK domestic mains supply

Approximately $230\,\text{V}$.

Three wires in a mains cable

Live, neutral, and earth.

Live wire color

Brown.

Neutral wire color

Blue.

Earth wire color

Green and yellow stripes.

Live wire function

Carries the alternating potential difference from the supply.

Neutral wire function

Completes the circuit and is at or close to $0\,\text{V}$.

Earth wire function

A safety wire that carries current if there is a fault, helping prevent the appliance case becoming live.

Potential difference between live and earth

About $230\,\text{V}$ in UK mains.

Earth wire potential

$0\,\text{V}$.

Earth wire current

Normally carries current only when there is a fault.

Open mains switch live wire danger

The live wire can still be dangerous because it can remain at a high potential difference relative to earth.

Live to earth connection danger

A very large current may flow, causing electric shock, heating, or fire.

Electrical power

The rate at which electrical energy is transferred.

Equation linking power, potential difference, and current

$P = V \times I$.

Equation linking power, current, and resistance

$P = I^2 \times R$.

Watt ($\text{W}$)

The unit of electrical power.

Higher-power appliance

Transfers more energy each second compared to a lower-power appliance.

Factors determining energy transferred by an appliance

Its power rating and how long it is switched on.

Equation linking energy transferred, power, and time

$E = P \times t$.

Equation linking energy transferred, charge flow, and potential difference

$E = Q \times V$.

Joule ($\text{J}$)

The unit of energy transferred.

Reason charge transfers energy in a circuit

Work is done when charge moves through a potential difference.

Energy transfer in an electric motor

Electrical energy is transferred mainly to the kinetic energy store of the motor and its load.

Energy transfer in an electric heater

Electrical energy is transferred mainly to thermal energy stores.

The National Grid

A system of cables and transformers that transfers electrical power from power stations to consumers.

High potential difference transmission in National Grid

For a given power, a higher potential difference means a lower current, reducing energy losses from heating in the cables.

Step-up transformer

Increases potential difference for transmission in the National Grid.

Step-down transformer

Decreases potential difference to safer, useful values for consumers in the National Grid.

Heating in transmission cables

Occurs because cable resistance causes electrical energy to be transferred to thermal energy stores when current flows.

Transmission loss reduction

Heating losses depend strongly on current, so a smaller current reduces energy dissipated in the cables.

First step in a circuit calculation

Identify the quantities given, write the correct equation, and include units.

Rearrangement of $V = I \times R$ for current

$I = \frac{V}{R}$.

Rearrangement of $V = I \times R$ for resistance

$R = \frac{V}{I}$.

Rearrangement of $Q = I \times t$ for current

$I = \frac{Q}{t}$.

Rearrangement of $Q = I \times t$ for time

$t = \frac{Q}{I}$.

Rearrangement of $P = V \times I$ for current

$I = \frac{P}{V}$.

Rearrangement of $E = P \times t$ for time

$t = \frac{E}{P}$.

Rearrangement of $E = Q \times V$ for charge

$Q = \frac{E}{V}$.

Interpreting circuit diagrams

Trace whether components share one path or separate branches, then apply the correct series or parallel rules.

Reading an I-V graph

Check which quantity is on each axis and use the shape to identify whether resistance is constant or changing.