You are leading a technical team at a company that is redesigning the cathode ra

Question

You are leading a technical team at a company that is redesigning the cathode ray tubes (CRT’s) used for computer monitors. To introduce this project to a group of stockholders, you need to demonstrate how an electron beam can be moved across a screen by a magnetic field. You decide to use an ordinary bar magnet held outside of the CRT to deflect the electrons. Before you do the demonstration, you need to know the qualitative effect of bringing a bar magnet up to a CRT. In the laboratory you qualitatively determine how the direction and size of the electron deflection is related to the magnetic field direction, the magnetic field strength, and the velocity of the electron. You also determine how the deflection is affected by how close the magnet is held to the CRT.

If you bring the north end of a magnet near the side of the CRT, which arrow represents the deflection of the electron beam on the screen?

Does the size of the deflection increase or decrease as the magnet gets closer to the CRT? As you increase the size of the magnetic field? Does the size of the deflection depend on the speed of the electrons? Explain your reasoning.

Explanation / Answer

if you bring the North pole near to CRT and we assume t that election has velocity in out of the page direction then force on electron

F = q*(VxB ) = -e*(VxB )

it will be downward so deflection will be vertical downward

and we know that deflection depends on speed and field strength

the angles of deflection are altered by varying the strengths of the coils, rather than physically moving them.

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