Charge-to-Mass Ratio of Electron in Circular Path

[Masafi]

electron is deflected in a circular path

electron speed = 2.7 x 10^8 m/s
diameter = 3cm
magnetic field = 0.24T

1. work out charge to mass ratio - 7.5 x 10^10

2. the textbook value is 1.76 x 10^11 - comment on this value

The answer is given as electron traveling close to speed of light so relativistic effects increases mass.

But increasing the mass will decrease the charge to mass ratio, rather than increase it. Which is what is given by the textbook value...

 

[Gear300]

What is the question?

 

[Masafi]

What is the question?

The textbook value is higher, after taking into account of relatavistic effects, i.e. mass increasing.

increasing the mass should decrease the value of e/m

not increase it - which is what has happened there. Why is that?

 

[Gear300]

Guess I didn't read the post well enough. This might not be helpful, but perhaps they used m/q instead. You can check through the formulations described in here: http://en.wikipedia.org/wiki/Relativistic_mass