11. Which component of the tubehead aims and shapes the x-ray beam? a. Metal housing b. Tubehead seal c. Aluminum disks d. Position-indicating device A B C D 12. __ is the measurement of the number of electrons moving through a conductor. a. Alternating current b. Direct current c. Amperage d. Voltage A B C D

11. **D** - Position-indicating device (PID). The PID is the part of the tubehead that extends from the metal housing and allows the operator to aim and shape the x-ray beam. The metal housing contains the x-ray tube, while the tubehead seal prevents leakage of oil. Aluminum disks filter out longer wavelength x-rays.<br /><br />12. **C** - Amperage. Amperage (measured in amperes) is the unit used to describe the rate of electrical current flow. Voltage is the electrical force that causes electrons to move, while alternating current (AC) and direct current (DC) describe the *direction* of electron flow.<br />