Charge-to-Mass Ratio of Electron in Circular Path

AI Thread Summary
The discussion focuses on calculating the charge-to-mass ratio of an electron moving in a circular path under a magnetic field, yielding a value of 7.5 x 10^10, which contrasts with the textbook value of 1.76 x 10^11. The discrepancy arises from relativistic effects, where the electron's speed approaches that of light, increasing its mass. However, this increase in mass should theoretically decrease the charge-to-mass ratio, leading to confusion over the higher textbook value. Participants suggest that the textbook may have used a different formulation, possibly m/q, to arrive at its figure. The conversation highlights the complexities of relativistic physics in calculating fundamental constants.
Masafi
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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...
 
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What is the question?
 
Gear300 said:
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?
 
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