Electrical circuits

Describe the structure of the atom, limited to the position, mass and charge of protons, neutrons and electrons

Protons (mass 1, charge +1) and neutrons (mass 1, charge 0) are located in the central nucleus, while electrons (negligible mass, charge -1) orbit outside the nucleus.

Draw and use electric circuit diagrams representing them with standard symbols

Circuit paths are drawn using straight black lines, representing specific component symbols like a long and short line for a cell, a rectangle for a resistor, a circle with an 'A' for an ammeter, and a circle with a 'V' for a voltmeter.

Recall that an ammeter is connected in series with a component to measure the current, in amps, in the component

An ammeter must be placed inline within the main circuit loop so that the full rate of electric charge flow passes directly through it.

Explain an electric current as the rate of flow of charge and the current in metals as a flow of electrons

Current measures how much electric charge passes a point per second, and inside metal wires this current consists of a physical sea of delocalised electrons flowing through the structure.

Recall and use the equation relating charge, current, and time

Charge = current x time (Q = It), where charge is measured in coulombs (C), current in amperes (A), and time in standard seconds (s).

Describe the differences between series and parallel circuits

A series circuit provides only a single continuous pathway for current to flow through all components sequentially, whereas a parallel circuit contains branches that split the current across multiple independent pathways.

Recall that current is conserved at a junction in a circuit

The total electric current entering a wire junction must exactly equal the total current leaving the junction because electrical charge cannot be created or destroyed.

Recall that a voltmeter is connected in parallel with a component to measure the potential difference (voltage), in volts, across it

A voltmeter must be wired across the terminals of a component to compare the difference in electrical potential energy between the two separate points.

Explain that potential difference (voltage) is the energy transferred per unit charge passed and hence that the volt is a joule per coulomb

Voltage measures how much work is done or energy is delivered by each package of charge moving through a component (V = E / Q).

Describe that when a closed circuit includes a source of potential difference there will be a current in the circuit

A complete conductive loop combined with a voltage source provides the necessary electrical push to cause free charges to move continuously.

Explain how changing the resistance in a circuit changes the current and how this can be achieved using a variable resistor

Increasing the circuit resistance reduces the current flow, which can be dynamically adjusted using a variable resistor to change the length of resistive wire inside the circuit path.

Recall and use the equation relating voltage, current, and resistance

Potential difference = current x resistance (V = IR), where potential difference is in volts (V), current in amperes (A), and resistance in ohms (Omega).

Explain why, if two resistors are in series, the net resistance is increased, whereas with two in parallel the net resistance is decreased

Series connection increases the total length of resistive material the current must push through, while parallel connection opens up alternative branches which increases the total pathway area for charge to flow.

Calculate the currents, potential differences and resistances in series circuits

The current remains identical at all points, the total source voltage is shared across the components, and the total resistance is found by adding the individual resistance values together (Rtotal = R1 + R2).

Describe the core practical method to construct and test series and parallel circuits using resistors and filament lamps

Build a single series loop with ammeters and voltmeters to record data, then reconstruct the circuit with parallel branches, comparing how the voltage drops and branch currents alter using the equation V = IR.

Describe power as the energy transferred per second and recall that it is measured in watt

Power measures the rate of total energy transformation or work done by an electrical component over time, with one watt equivalent to one joule per second.

Recall and use the equation for electrical power in terms of energy and time

Power = energy transferred / time taken (P = E / t), where power is in watts (W), energy is in joules (J), and time is in seconds (s).

Recall and use the equation for electrical power in terms of current and potential difference

Power = current x potential difference (P = I x V), where power is measured in watts (W), current in amperes (A), and potential difference in volts (V).

Explain the difference between direct and alternating voltage

A direct voltage remains at a constant polarity forcing current in one continuous path, whereas an alternating voltage continuously oscillates its positive and negative terminals to shift the electrical path back and forth.

Describe direct current (d.c.) and recall a common source

Direct current is the movement of electrical charge in one uniform direction only, and it is typically supplied by chemical cells and standard batteries.

Describe alternating current (a.c.)

Alternating current is a type of electrical flow where the movement of charge periodically reverses its direction entirely at a set frequency.

Recall the parameters of the domestic electricity supply in the UK

The UK mains domestic supply runs on an alternating current system with a frequency of 50 Hz and an effective voltage of approximately 230 V.

Explain the difference in function between the live and the neutral mains input wires

The live wire carries the alternating high voltage into the appliance from the source, while the neutral wire completes the electrical loop by returning the current back to the grid at approximately zero voltage.

Explain the function of an earth wire and of fuses or circuit breakers in ensuring safety

The earth wire provides a low-resistance path to the ground for fault currents, while a fuse or circuit breaker automatically melts or trips to break the path completely if the current spikes too high.

Explain why switches and fuses should be connected in the live wire of a domestic circuit

Placing them in the live wire ensures that when a fuse blows or a switch is opened, the high-voltage supply is cut off from the internal components of the appliance entirely.

Recall the potential differences between the live, neutral and earth mains wires

The potential difference between live and neutral is 230 V, between live and earth is 230 V under normal operations, and between neutral and earth is approximately 0 V.

Explain the dangers of providing any connection between the live wire and earth

Creating a pathway between the live wire and earth causes a massive, rapid surge of current which can cause severe electrical fires or fatal electric shocks if passed through a person.

Describe the relationship between the power ratings for domestic electrical appliances and the changes in stored energy when they are in use

A higher power rating means the appliance transfers energy out of its electrical storage supply into other configurations much faster per second than a device with a lower rating.