Which transformer is used to increase voltage from 110V to over 60,000 volts?

The correct choice is the step-up transformer, which is specifically designed to increase voltage levels from a lower voltage to a significantly higher voltage. In the context of dental radiography, a step-up transformer converts the standard line voltage, such as 110 volts, to a much higher voltage required for X-ray production, often exceeding 60,000 volts. This process is essential as it allows the tube to generate the high energy necessary to produce X-rays effectively.

The mechanism of a step-up transformer involves a primary coil and a secondary coil, where the number of turns in the secondary coil is greater than in the primary coil. This design principle increases the voltage while decreasing the current, which is ideal for the operation of X-ray equipment.

Other devices mentioned, such as a step-down transformer, would serve the opposite function of reducing voltage, while an autotransformer adjusts voltage levels but does not necessarily increase it to such high levels like 60,000 volts. A voltage regulator maintains voltage levels within a specific range but does not transform voltages as a step-up transformer does. Therefore, the step-up transformer is crucial for applications requiring high voltages, such as those found in dental radiography.