In a mass spectrometer, an ion of charge, q, and mass, m, moving in a path of radius, r, in a field of flux density, B, has a speed of
A
\(\frac{qBr}{m}\)
B
\(\frac{mr}{qB}\)
C
\(\frac{qm}{Br}\)
D
\(\frac{mq}{r}\)
Verified Correct Answer: A.
Physical Principles & Numerical Solution
F = qvB ( force on moving charge in a magnetic field) F = \(\frac{mv^2}{r}\)
equating F
qvB = \(\frac{mv^2}{r}\)
qB = \(\frac{mv}{r}\)
qBr = mv
Therefore, v = \(\frac{qBr}{m}\)
Source: Myschool Past Questions Archive (Record #69359)