LEDs (Light Emitting Diodes) are semiconductor devices that emit light when current flows through them in the forward direction. When connected correctly in a circuit with the anode (+) connected to the positive voltage and the cathode (-) to the negative voltage (assuming it’s a DC circuit), LEDs illuminate as electrons recombine with electron holes within the semiconductor material, emitting photons of light. However, if LEDs are connected in reverse polarity, meaning the anode and cathode are swapped, they typically do not conduct current and do not emit light.
Operating an LED in reverse bias, where the polarity is reversed compared to its intended forward operation, results in minimal or no current flow through the LED. LEDs are designed with a built-in junction that only allows current to flow in one direction (forward bias), facilitating light emission. In reverse bias, this junction blocks current flow, preventing the LED from lighting up. Moreover, applying reverse voltage beyond the LED’s maximum reverse voltage rating can potentially damage the LED permanently, leading to failure or reduced performance over time.
When LEDs are wired incorrectly, such as connecting the anode to the negative side and the cathode to the positive side of a DC power supply, they do not illuminate due to the absence of current flow through the LED in the forward direction. This incorrect wiring scenario typically results in no visible light output from the LED. In some cases, if the reverse voltage applied exceeds the LED’s maximum reverse voltage rating, it can cause irreversible damage to the LED by breaking down its internal junction or damaging the semiconductor materials, rendering the LED unusable.
Therefore, to ensure proper operation and longevity of LEDs, it is crucial to observe the correct polarity when connecting them in circuits. LEDs are designed for specific forward voltage and current ratings, and observing these specifications ensures optimal performance and reliability in various lighting and electronic applications.