ASNT Industrial Radiography Radiation Safety Practice Test

What happens to free electrons when the milliamperes are increased in an X-ray tube?

1. They decrease

2. They remain unchanged

3. They increase in number

4. They are entirely used up

The correct answer is: They increase in number

When the milliamperes (mA) in an X-ray tube are increased, the number of free electrons available for the X-ray production also increases. This is because the mA setting controls the current flowing through the tube, which in turn determines the number of electrons that are emitted from the cathode. As the current increases, more electrons are generated and made available to be accelerated towards the anode. The increase in free electrons leads to a higher rate of X-ray photon production when these electrons collide with the anode material. This process enhances the overall intensity of the X-ray beam produced, which is vital for various imaging and therapeutic applications in radiography. Thus, increasing the milliamperes effectively increases the number of free electrons that contribute to generating X-rays.