CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Internal Resistance and Potential Dividers
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Deformation of Solids
Thermal Physics
Uniform Circular Motion
Simple Harmonic Motion
The Nucleus and Radioactive Decay
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Fundamental Particles
Conservation laws
- 3 things to know
- Unit A2 2
Overview
Recall questions on conserving charge, lepton number and baryon number, the values assigned to a baryon, an antibaryon, a lepton and an antilepton, the baryon number of a single quark, checking all three for the decay of a neutron, why an antineutrino accompanies an electron, and using the rules to test whether a proposed interaction is allowed.
What you need to know
Answer each one before you reveal it.
State the rule for conservation of charge.
What baryon number is assigned to a baryon, to an antibaryon and to any other particle?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Name the three quantities that must be conserved in every particle interaction at this level.
Model answer
Charge, lepton number and baryon number.
- 2
State the rule for conservation of charge.
Model answer
The total charge before an interaction must equal the total charge after it.
- 3
What baryon number is assigned to a baryon, to an antibaryon and to any other particle?
Model answer
Plus one for a baryon, minus one for an antibaryon, and zero for mesons, leptons and gauge bosons.
- 4
What baryon number does a single quark carry?
Model answer
Plus one third, so that three of them give a baryon number of one.
- 5
What lepton number is assigned to a lepton, to an antilepton and to any other particle?
Model answer
Plus one for a lepton, minus one for an antilepton, and zero for everything that is not a lepton.
- 6
Why is lepton number conserved separately from baryon number?
Model answer
They are independent quantum numbers, and no observed interaction converts a lepton into a baryon or the reverse.
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