What type of electrical equipment is used to change voltage level or waveform?

The most appropriate answer for changing voltage levels or waveform is a transformer. A transformer is a device specifically designed to transfer electrical energy between two or more circuits through electromagnetic induction, allowing for the adjustment of voltage levels while maintaining the same frequency.

Transformers can step up (increase) or step down (decrease) voltage levels depending on their design, making them essential in power distribution systems. They work by utilizing coils of wire wrapped around a magnetic core, facilitating the transfer of energy from the primary coil to the secondary coil while changing the voltage level as needed.

The other options serve different functions: a rectifier converts alternating current (AC) to direct current (DC), an inverter does the opposite by converting DC back to AC, and a conductor is simply a material that allows the flow of electrical current. Hence, while they all relate to electrical systems, only the transformer directly changes voltage levels without altering the fundamental electrical characteristics in a way that doesn't apply to waveform conversion like the other devices do.