Before the advent of today’s flat-screen televisions, the TV picture was "painted" on the screen of a cathode ray tube (also called a picture tube) by an electron beam that was steered by the magnetic force from a magnetic field produced by coils carrying a varying current. If the electron beam is first accelerated through a 25.0-V potential difference, and then passed through a magnetic field oriented at right angles to the beam, what field strength would be needed for the electrons to follow a circular arc with curvature radius 7.12 cm?