An electron shot from the back of a T.V. help?

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In summary, the conversation discusses the calculation of the magnetic field required for an electron to make a circular path with a radius of 30m when shot from the back of a TV towards the front at half the speed of light. The correct calculation for the magnetic field is B = 3.06x10^-5 and the conversation also mentions taking "baby steps" to arrive at the correct calculation.
  • #1
acsis
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Homework Statement



If I shoot an electron from the back of a TV at a screen towards the front at .5c (e= speed of light) What magnetic field must be in the coils around the cathode ray tube (picture tube) if the electron would have made a circle radius 30m if it hadn't hit the screen and made it glow. (your TV show)

Homework Equations



r= (mv)/qB

The Attempt at a Solution



Using the equation rearranged to solve for B:

B=mv/qr

mass of an electron = 9.1 x 10^-31
charge of an electron = 1.602 x 10^-19
.5c=...well it's half of the spd of light so I assume : 1.5 x 10^8 since the spd of light is 3x10^8 if I remember correctly.
and radius = 30m

so:

B= (9.1x10^-31)(1.5x10^8)/(1.602x10^-19)(30)
B= .026?

Could someone check if I did this correctly, did I forget something?
 
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  • #2
Your calculation is wrong. Check it.
 
  • #3
Hm.

Now I'm getting

B = 3.06x10^-5

Is that correct?

I tried taking baby steps to see what I did incorrectly but I'm not sure if it's helping.
 
  • #4
Yes. It is correct.
 
  • #5
Thanks, now I know those baby steps helped.
 
  • #6
acsis said:
Hm.

Now I'm getting

B = 3.06x10^-5

Is that correct?

I tried taking baby steps to see what I did incorrectly but I'm not sure if it's helping.

Have checked those calculations and got 2.8402x10^-5... :uhh:
 

1. What causes an electron to be shot from the back of a T.V.?

An electron is shot from the back of a T.V. due to the process of electron emission, which occurs when a high voltage is applied to a metal electrode inside the T.V. tube. This causes the electrons to gain enough energy to be released from the metal surface and travel towards the screen, creating the images we see on the T.V. screen.

2. Is it dangerous to have electrons being shot from the back of a T.V.?

No, it is not dangerous to have electrons being shot from the back of a T.V. The electrons are contained within the T.V. tube and do not pose a threat to anyone watching the T.V. Additionally, modern T.V.s have safety features in place to prevent any potential hazards.

3. How fast do electrons travel when being shot from the back of a T.V.?

Electrons can travel at speeds up to 99% of the speed of light when being shot from the back of a T.V. This is incredibly fast and allows the electrons to reach the screen in a matter of milliseconds, creating the images we see on the T.V.

4. Can electrons be shot from the back of a T.V. in any direction?

No, electrons can only be shot from the back of a T.V. in a specific direction towards the screen. This is due to the design of the T.V. tube and the electrodes within it, which only allow for the electrons to be emitted in a specific direction.

5. How does the T.V. control the direction of the electrons being shot from the back?

The T.V. controls the direction of the electrons being shot from the back by using electromagnets to manipulate the electron beam. These electromagnets are located around the T.V. tube and can adjust the path of the electrons to create the images we see on the screen.

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