The generator is responsible for stepping up the voltage from hundreds of volts to thousands and even hundred thousands of volts. At the control console, there is a kVp selector. When you select the kVp on the control console, you are selecting the energy level, or QUALITY, of the x-ray beam being produced. The higher the kVp, the higher the x-ray energy is. When you increase the kVp, you increase the penetrating ability of the x-ray beam. Since the x-ray beam energy is higher, more x-rays will make it's way through the patient and onto the image receptor. You have now seen the 2 "Q" words that you will have to become familiar with. mAs controls Quantity and kVp controls QUALITY. When you increase the kVp, you increase the quality of the beam.
So why is kVp important? As we went over earlier, there are 2 aspects that create an image. The density (overall darkness) and contrast (grayness).
Below is an example of what happens when you increase kVp. Notice how one image appears more gray? Increasing kVp has this effect. Decreasing kVp will make an image appear more black and white (less gray). Image A would be the appearance of a knee x-ray at 60 kVp. Image B would happen if you were to use 75 kVp.