Magnetic Field Practice Problems Fig 1 shows a mass spectrometer. It is used to

Question

Magnetic Field Practice Problems Fig 1 shows a mass spectrometer. It is used to measure the charge to mass ratios of different ions. The sample is ionized and then accelerated through a potential difference Delta V and then they enter a region of uniform magnetic field. The field bends the ions into circular trajectories. After traveling a half circle they strike the wall or a small opening into the detector. As the potential difference changes, different ions make it into the detector. Typical values are B = 0.20 T, and the distance between entrance and exit holes d = 8.00 cm. What potential difference Delta V is needed to detect N_2+ O_2 CO^+ Given significant figures you can find and were given, what is the size of the hole of the detector you'd make?

Explanation / Answer

Mass of a molecule = m, charge = q
radius of circle in the magnetic field = r = d/r
Inital KE = qV = 0.5mv^2
v = sqroot(2qV/m)

Magnetic force, F = qvB = mv^2/r
qB = sqroot(2qVm)/r
2qVm = (rqB)^2
V = (rqB)^2/2qm = d^2B^2*q/8*m = 0.08^2*0.2^2*1.6*10^(-19)/8m = 51.2*10^-25/m

1. V = 51.2*10^-25/28*1.6*10^-27 = 114.285V
2. V = 51.2*10^-25/32*1.6*10^-27 = 100 V
3. V = 51.2*10^-25/28*1.6*10^-27 = 114.285 V

Related Questions

Navigate

• Browse (All)
• Browse M
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.