What type of electrical component is used to provide steady direct current while minimizing radio interference?

The correct answer is a capacitor. Capacitors play a crucial role in electrical systems by providing smoothing or filtering of electrical signals. When it comes to steady direct current (DC) applications, capacitors can store energy and release it in a controlled manner, effectively reducing voltage fluctuations and providing a more stable output.

In the context of minimizing radio interference, capacitors can filter out high-frequency noise that might otherwise affect sensitive electronic equipment. By smoothing out the ripples in the DC supply, capacitors help maintain a steady voltage level while reducing electromagnetic interference, which can interfere with radio frequency signals.

While relays are used for switching and controlling circuits, they are not designed for smoothing DC current or filtering interference. Inductors store energy in a magnetic field and can also be used for filtering, but they primarily work with alternating current (AC) rather than DC. Transformers are used to change voltage levels and do not provide steady DC output. Thus, a capacitor is the most effective component for these purposes.