U = q U = q V. Sample Problem: In a cathode ray tube (CRT, like in your TV or computer monitor) electrons initially at rest are accelerated through a potential difference of 10 kV. What is their final speed? U = q V. Sample Problem: In a cathode ray tube (CRT, like in your TV or computer monitor) electrons initially at rest are accelerated through a potential difference of 10 kV. What is their final speed?