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OpenStem
@openstem · Joined Jul 2026
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Quiz8 questions
For a reversible isothermal process at temperature T that absorbs heat Q, what is the entropy change of the system?
AΔS = QTBΔS = Q/TCΔS = T/QDΔS = 0, since energy is conserved
Physics · L4 · Entropy & Heat Engines — 8 Q
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Physics · L4 · Entropy & Heat Engines — 8 QQuiz7 questions
A sample contains 800 g of a radioisotope with a half-life of 6 hours. How much remains after 18 hours?
A100 gB200 gC400 gD50 g
Physics · L4 · Nuclear Physics — 7 Q
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Physics · L4 · Nuclear Physics — 7 QQuiz8 questions
Which Maxwell equation directly implies that magnetic monopoles do not exist?
AGauss's law for electricityBGauss's law for magnetismCFaraday's lawDThe Ampère-Maxwell law
Physics · L4 · Maxwell's Equations & EM Waves
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Physics · L4 · Maxwell's Equations & EM WavesQuiz8 questions
What distinguishes polarized light from unpolarized light?
APolarized light has a higher frequencyBPolarized light's electric field oscillates in a single fixed plane; unpolarized light's field direction is randomCPolarized light travels faster than unpolarized lightDPolarized light is always monochromatic
Physics · L4 · Polarization & Diffraction
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Physics · L4 · Polarization & DiffractionQuiz7 questions
A long straight wire carries 4 A. What is the magnetic field magnitude 2 cm away? (μ₀ = 4π × 10⁻⁷ T·m/A)
A2 × 10⁻⁵ TB4 × 10⁻⁵ TC8 × 10⁻⁵ TD1.6 × 10⁻⁴ T
Physics · L4 · Magnetism — 7 Q
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Physics · L4 · Magnetism — 7 QQuiz7 questions
Kirchhoff's current law is a direct consequence of which conservation principle?
AConservation of energyBConservation of chargeCConservation of momentumDConservation of magnetic flux
Physics · L4 · DC Circuits — 7 Q
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Physics · L4 · DC Circuits — 7 QQuiz7 questions
A gas is heated at constant volume from 200 K to 400 K. What happens to its pressure?
AIt halvesBIt stays the sameCIt doublesDIt quadruples
Physics · L4 · Kinetic Theory of Gases — 7 Q
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Physics · L4 · Kinetic Theory of Gases — 7 QQuiz7 questions
If the distance between two masses triples, by what factor does the gravitational force between them change?
AIt becomes 1/3 as strongBIt becomes 1/9 as strongCIt becomes 3× as strongDIt is unchanged
Physics · L4 · Gravitation & Orbital Mechanics — 7 Q
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Physics · L4 · Gravitation & Orbital Mechanics — 7 QQuiz7 questions
A wire of length 2 m stretches to 2.004 m under load. What is the strain?
A0.0002B0.002C0.02D0.2
Physics · L4 · Elasticity — 7 Q
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Physics · L4 · Elasticity — 7 QQuiz7 questions
Sound generally travels fastest in which type of medium?
AVacuumBGasesCLiquidsDSolids
Physics · L4 · Sound Waves & the Doppler Effect — 7 Q
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Physics · L4 · Sound Waves & the Doppler Effect — 7 QQuiz7 questions
Doubling the thickness of an insulating wall, all else equal, does what to the conductive heat-loss rate?
ADoubles itBHalves itCLeaves it unchangedDQuadruples it
Physics · L4 · Heat Transfer — 7 Q
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Physics · L4 · Heat Transfer — 7 QQuiz7 questions
Doubling the plate separation of a parallel-plate capacitor, all else fixed, does what to its capacitance?
ADoubles itBHalves itCQuadruples itDLeaves it unchanged
Physics · L4 · Capacitance & Dielectrics — 7 Q
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Physics · L4 · Capacitance & Dielectrics — 7 QQuiz3 questions
The time-dependent Schrödinger equation in Dirac notation is:
Aiℏ ∂|ψ⟩/∂t = p̂²|ψ⟩/2mB−iℏ ∂|ψ⟩/∂t = Ĥ|ψ⟩Ciℏ ∂|ψ⟩/∂t = Ĥ|ψ⟩Dℏ ∂|ψ⟩/∂t = Ĥ|ψ⟩
Physics · L5 · Formal Quantum Mechanics
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Physics · L5 · Formal Quantum MechanicsQuiz3 questions
In the canonical ensemble, the mean energy ⟨E⟩ is expressed in terms of the partition function Z as:
A⟨E⟩ = ∂ ln Z/∂βB⟨E⟩ = −k_B T ln ZC⟨E⟩ = ln Z / βD⟨E⟩ = −∂ ln Z/∂β
Physics · L5 · Statistical Mechanics
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Physics · L5 · Statistical MechanicsQuiz8 questions
Bloch's theorem states that an electron eigenstate in a periodic potential takes the form:
Aψ(r) = A sin(kr), independent of the latticeBψ_k(r) = e^{ik·r} u_k(r), with u_k periodic in the latticeCψ(r) = Σ c_n φ_n(r), a fixed sum of atomic orbitals onlyDψ_k(r) = e^{-r²/2σ²}, a localised Gaussian packet
Physics · L5 · Condensed Matter Physics
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Physics · L5 · Condensed Matter PhysicsQuiz8 questions
Which of the following is NOT a fundamental fermion in the Standard Model?
AElectronBUp quarkCPhotonDMuon neutrino
Physics · L5 · Particle Physics
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Physics · L5 · Particle PhysicsQuiz7 questions
A chaotic system's sensitive dependence on initial conditions means that the separation δ(t) between two initially nearby trajectories grows:
ALinearly in time: δ(t) ∝ tBExponentially in time: δ(t) ∝ e^(λt), λ > 0CNot at all — chaotic trajectories stay close foreverDOnly in systems with explicit random noise added
Physics · L5 · Nonlinear Dynamics & Chaos
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Physics · L5 · Nonlinear Dynamics & ChaosQuiz8 questions
The electromagnetic field tensor F^μν is defined in terms of the four-potential A^μ as:
A∂^μA^ν + ∂^νA^μB∂^μA^ν − ∂^νA^μCA^μA^νD∂_μ∂^μA^ν
Physics · L5 · Covariant Electrodynamics
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Physics · L5 · Covariant ElectrodynamicsQuiz8 questions
An order parameter is a quantity that is:
ANonzero in both phases, but larger in the ordered phaseBZero in the disordered phase and nonzero in the ordered phaseCAlways equal to the temperature TDOnly defined for first-order transitions
Physics · L5 · Phase Transitions & Critical Phenomena
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Physics · L5 · Phase Transitions & Critical PhenomenaQuiz8 questions
In quantum field theory, what is treated as the fundamental physical object?
AThe particle, as a point object with a definite trajectoryBThe field, defined at every point of spacetime, with particles as its quantized excitationsCThe wavefunction on a fixed configuration spaceDThe spacetime metric alone
Physics · L5 · Quantum Field Theory: Fields, Propagators & Feynman Diagrams
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Physics · L5 · Quantum Field Theory: Fields, Propagators & Feynman DiagramsQuiz6 questions
In non-degenerate time-independent perturbation theory, the first-order energy correction E_n⁽¹⁾ equals:
AThe sum over all other states of the coupling matrix elementB⟨n⁽⁰⁾|H'|n⁽⁰⁾⟩, the expectation value of H' in the unperturbed stateCZero, alwaysDThe unperturbed energy E_n⁽⁰⁾ itself
Physics · L5 · Perturbation Theory & Scattering
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Physics · L5 · Perturbation Theory & ScatteringQuiz6 questions
The cosmological principle assumes the universe is, on large scales:
AStatic and unchangingBHomogeneous and isotropicCCentered on the Milky WayDInfinitely dense everywhere
Physics · L5 · Cosmology
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Physics · L5 · CosmologyQuiz6 questions
Which of these is NOT one of the two defining experimental signatures of superconductivity?
AZero DC electrical resistance below T_cBThe Meissner effect (active flux expulsion)CInfinite thermal conductivityDBoth zero resistance and the Meissner effect together
Physics · L5 · Superconductivity
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Physics · L5 · SuperconductivityQuiz6 questions
A qubit state |ψ⟩ = α|0⟩ + β|1⟩ differs from a classical bit primarily because:
AIt can only take the values 0 or 1, just like a classical bitBIt can exist in a continuum of superpositions before measurementCIt has no physical realisationDIt always has α = β
Physics · L5 · Quantum Information
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Physics · L5 · Quantum InformationQuiz6 questions
A local gauge symmetry differs from a global symmetry in that:
AIt applies only to fermions, never bosonsBThe transformation parameter can vary independently at every spacetime pointCIt cannot be spontaneously brokenDIt has no associated conserved current
Physics · L5 · Gauge Theories & the Higgs Mechanism
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Physics · L5 · Gauge Theories & the Higgs MechanismQuiz6 questions
What primarily distinguishes a plasma from an ordinary ionised gas that is not considered 'a plasma'?
AA plasma has no free chargesBA plasma exhibits collective behaviour from long-range electromagnetic coupling between particlesCA plasma must be at absolute zero temperatureDThere is no meaningful distinction
Physics · L5 · Plasma Physics
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Physics · L5 · Plasma PhysicsQuiz6 questions
In the path integral formulation, the quantum amplitude between two points is:
AThe amplitude of the single classical path onlyBA sum over every possible path, each weighted by e^(iS/ħ)CIndependent of the action S entirelyDOnly defined for free particles
Physics · L5 · The Path Integral Formulation
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Physics · L5 · The Path Integral FormulationQuiz6 questions
Fusion occurs in stellar cores despite thermal energies being far below the Coulomb barrier because:
AStellar cores are actually hotter than the Coulomb barrier energyBQuantum tunnelling allows a nonzero fusion probability even below the classical barrierCThe Coulomb barrier does not apply inside starsDGravity directly forces nuclei to fuse regardless of charge
Physics · L5 · Nuclear Astrophysics
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Physics · L5 · Nuclear AstrophysicsQuiz6 questions
A single mode of the quantised electromagnetic field is mathematically equivalent to:
AA free particleBA quantum harmonic oscillatorCA rigid rotorDA two-level atom only
Physics · L5 · Quantum Optics
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Physics · L5 · Quantum OpticsNote~142 words · 1 min
Light travels in straight lines Block it with something solid and a dark patch appears behind: a shadow. Shadows change through the day Try it: hold your hand in front of a torch. The dark shape on the wall is exactly where your hand stoppe
Physics · L1 · Light and Shadow
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Physics · L1 · Light and Shadow