uniform circular motion and magnetic force

[mcgill2012]

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can anyone clarify why an electron experiencing magnetic force in which B field is perpendicular to qv vector undergoes uniform circular motion? and why does this mean that increasing B field strength will decrease radius of orbit but not increase velocity?

 

[PiBond]

can anyone clarify why an electron experiencing magnetic force in which B field is perpendicular to qv vector undergoes uniform circular motion? and why does this mean that increasing B field strength will decrease radius of orbit but not increase velocity?

qvB = mv^2/r

increasing B field means we increase the left side of the equation (so right side has to increase proportionally) and the B field is providing a force which upon increasing that force will cause the radius to decrease.

the B field is providing a force perpendicular to the velocity, thus linear speed won't increase or decrease. this translates to an increase/decrease in radius instead

the right hand rule will show how the force of the B field and the velocity of the electron are perpendicular, thus causing the uniform circular motion