General Certificate of Secondary Education (GCSE) Design Technology Practice Exam

The components used in series to create a time delay typically include a resistor, a capacitor, and sometimes a transistor. In this configuration, the resistor and capacitor form an RC (resistor-capacitor) circuit, which is fundamental for timing applications.

When a voltage is applied to the series circuit, the capacitor starts to charge through the resistor. The time it takes for the capacitor to charge to a certain voltage level (often about 63% of the supply voltage) is determined by the product of the resistance and the capacitance (known as the time constant, τ = RC). This time constant is critical for applications where a delay is necessary, such as in timers or for creating specific signal delays in electronic circuits.

The inclusion of a transistor in the circuit can provide control over the discharge of the capacitor or enhance switching capabilities, which may be part of a more complex timing circuit. Therefore, this combination effectively utilizes the charge and discharge characteristics of the capacitor, influenced by the resistor, to derive a predictable timing effect.

The other combinations of components listed do not provide the same fundamental time delay functionality as the resistor-capacitor configuration, which is why the resistor, capacitor, and transistor setup is the most suitable choice for creating a time delay in a