How Many Electrons Strike the Screen in 1 Hour?

[coolnufc]

The beam current in a television tube is 32mA. The electrons travel at a speed of 4.2x10^7m/s through a distance 21cm.

a) The number of electrons striking the screen in 1 hour is?

I did: Q=IT = 0.032A x (60x60)s = 115.2 C

Number of electrons = 115.2/1.6x10^-19 = 7.2x10^20

b) The number of electrons in the beam at any instant is?

I tried doing the same as above but for one seconds but couldn't work it out at all. Anyone give me a clue?

 

[LowlyPion]

The length of your beam is .21 m.

In 1 sec you would have a beam column containing of .032ma.

A 1 sec column would contain 3.2*10^-5*6.241*10¹⁸ electrons of which only .21/4.2*10⁷ are actually in motion within the tube.

 

[nlightner]

To calculate the number of electrons in the beam at any instant, you would need to know the cross-sectional area of the beam. This would allow you to calculate the volume of the beam and then use the speed of the electrons to determine the number of electrons passing through that volume in one second. However, without this information, it is not possible to accurately determine the number of electrons in the beam at any instant.