How Many Electrons Strike the Screen in 1 Hour?

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The beam current in the television tube is 32 mA, resulting in a total charge of 115.2 C striking the screen in one hour. This charge translates to approximately 7.2 x 10^20 electrons. To determine the number of electrons in the beam at any instant, calculations involve the beam's length of 0.21 m and the speed of electrons at 4.2 x 10^7 m/s. The discussion highlights the challenge of calculating the number of electrons in motion within the tube over a one-second interval. Overall, the focus is on understanding electron flow and current in the context of a television tube.
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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?
 
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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.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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