What should the working voltage of a capacitor in an AC circuit exceed?

The working voltage of a capacitor in an AC circuit should exceed the applied voltage by a significant margin to ensure reliability and safety. Selecting a working voltage that is at least 50% more than the applied voltage provides a buffer against voltage spikes and fluctuations that are common in AC systems. This additional voltage rating helps to prevent dielectric breakdown and prolongs the capacitor's lifespan.

In AC circuits, voltage can vary significantly due to alternating current, and transients can occur which may temporarily increase the voltage beyond its steady state. By using capacitors rated for substantially higher voltages, one can mitigate the risk of failure due to these transient conditions. This practice is crucial for maintaining the integrity of the circuit and ensuring proper operation over time.

While other options suggest adding 10%, 25%, or 75% to the applied voltage, they do not offer the same level of safety and durability that a 50% margin provides in real-world applications. Therefore, selecting a capacitor with a working voltage that exceeds the applied voltage by 50% is a prudent engineering choice in AC circuits.