General Certificate of Secondary Education (GCSE) Design Technology Practice Exam 2025 - Free GCSE Design Technology Practice Questions and Study Guide

Using LEDs in series with a resistor is essential because it serves to prevent excess current that can lead to overheating and damage the LED. LEDs are designed to operate at a specific forward voltage and current. If the current flowing through them exceeds this limit, it can cause the LED to fail by burning out. The resistor acts as a current-limiting device; it reduces the amount of current that flows through the LED to a safe level.

In this setup, the resistor is calculated based on the supply voltage and the desired current for the LED, ensuring that the LED operates within its safe electrical parameters. Without the resistor, the LED would draw too much current, resulting in quick failure.

The other options revolve around different concepts. While increasing current flow and improving light intensity can be beneficial under the right circumstances, they are not the primary reason for using a resistor with an LED. Handling high voltage inputs is also irrelevant because LEDs usually operate on low voltage. Hence, the resistor is primarily there to safeguard the LED from damage caused by excessive current.