Mass Spectrometer
This video derives how a mass spectrometer determines the mass-to-charge ratio of a charged particle using its two main parts: the velocity selector and the deflection chamber. In the velocity selector, perpendicular (crossed) electric and magnetic fields exert independent forces on a moving charge; since the charge moves through at a constant velocity, these forces must balance, so only charges with velocity v = E/B pass straight through. In the deflection chamber, only the magnetic field remains, so the charge follows a circular path, with positive charges curving one way and negative charges the other, the magnetic force providing the centripetal force. Summing forces and substituting v = E/B gives the mass-to-charge ratio, m/q = RB²/E. Want Lecture Notes? http://www.flippingphysics.com/mass-s...
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Chapters:
0:00 Velocity Selector
4:29 Deflection Chamber
#MassSpectrometer #VelocitySelector #DeflectionChamber
Curriculum Standards:
AP Physics 2, Topic 12.2 Magnetism and Moving Charges
12.2.B.3: "In a region containing both a magnetic field and an electric field, a moving charged object will experience independent forces from each field."
AP Physics C: E&M, Topic 12.2 Magnetism and Moving Charges
12.2.B.2: "In a region containing both a magnetic field and an electric field, a moving charged object will experience independent forces from each field."
IB Physics, D.3 Motion in Electromagnetic Fields (Guidance): D.3 (Guidance) [Charge-to-Mass Ratio]: "The determination of the charge to mass ratio for a charged particle by investigating its path in a uniform magnetic field is required."
JEE Main & NEET, Unit 13 Magnetic Effects of Current and Magnetism
"Force on a moving charge in uniform magnetic and electric fields."
Ontario Physics (SPH4U), Strand D Gravitational, Electric, and Magnetic Fields
"D2.4 (SPH4U): Analyse, and solve problems involving, the force on charges moving in a uniform magnetic field (e.g., the force on a current-carrying conductor or a free electron)."
Ontario Physics (SPH4C), Strand D Electricity and Magnetism
"D2.4 (SPH4C): conduct an inquiry to determine the magnetic fields produced by a permanent magnet, a straight current-carrying conductor, and a solenoid, and illustrate their findings [PR, AI, C]"
Gaokao Physics, Selective Compulsory 2, 2.1 Magnetic Field
SC2.1.3: "Use the Lorentz force to analyze the circular motion of a charged particle in a uniform magnetic field. Understand its deflection and applications."
Australian Curriculum Physics, Unit 3: Gravity and Electromagnetism, Electromagnetism
ACSPH108: "Magnets, magnetic materials, moving charges and current-carrying wires experience a force in a magnetic field; this force is utilised in DC electric motors. Equations: F = BIl (force on a current-carrying wire); F = qvB (force on a charge moving in a magnetic field)."
MCAT, Foundational Concept 4E: Atoms, Nuclear Decay, Electronic Structure, and Atomic Chemical Behavior, Atomic Nucleus (PHY, GC): Mass Spectrometer: "Mass spectrometer."
Cambridge A Level (9702), 20.3 Force on a moving charge
20.3.5: "describe the motion of a charged particle moving in a uniform magnetic field perpendicular to the direction of motion of the particle."
20.3.6: "explain how electric and magnetic fields can be used in velocity selection."