The Cathode Ray tube

The following video demonstrates the classic "Maltese Cross" Cathode Ray Tube. The tube provides a simple, visual, introduction to Cathode Rays, including the demonstration of deflection of the rays by a magnetic field. In addition the video features some measurements of the current passing through the tube at different potential differences. These measurements allow you to:

• • Plot the electrical characteristics of the tube (graph of current against Potential difference).

  • Calculate the energy of the electrons at different voltages (using E = qV) and hence calculate their speeds (E = 1/2mv²).

  • Calculate the number of electrons passing through the tube each second at different voltages (current = charge per electron x electrons per second).

  • Calculate the power supplied to the tube (either using the numbers derived in response to the last two bullet points, or from P = IV).