URGENT - J J Thomsons experiment (1 Viewer)

[Mr_Kap]

Ok. I was looking through my textbook and other people's hsc resources and I found that there were two ways to perform thomson's experiment?

One method is that "he calculated the radius of the curved electron beam when deflected by the magnetic field only"

While the other method says "By equating the potential energy and kinetic energy of the electrons at the
cathode and anode respectively, and substituting the potential difference across the tube and the
velocity of the electrons, he was able to calculate the charge-to-mass ratio of the electron."

which one do the markers prefer?
Which one did you get taught at school?
Which one do i use?

 

[anomalousdecay]

When calculating the charge to mass ratio, you need to look at the potential energy and kinetic energy of the electrons, while also keeping in mind the radius of curvature of the path they followed.

Using:



you can find the charge to mass ratio as:

 

[Kaido]

Both of the methods you described are basically the same, the latter is more generalised and should not be used in an exam situation.
Follow anomaly's method above for ALL exam questions asking for this and you may also want to equate the ELECTRIC with MAGNETIC

 

[Mr_Kap]

Both of the methods you described are basically the same, the latter is more generalised and should not be used in an exam situation.
Follow anomaly's method above for ALL exam questions asking for this and you may also want to equate the ELECTRIC with MAGNETIC

Alright, thx. I know both ways so i just wanted to know which way to use...thx for the clarification.