Phys 102 – Lect. 29 Final exam review 1

Final exam study approaches How should you study for the physics exam? Cramming DOES NOT work Emphasize understanding concepts & problem solving, NOT memorization Review pre-lecture & lecture concepts Review problems: ACTs, HW, quizzes, practice exams Understand formula sheet (i.e. when to use and when NOT to use an eq.) & know what each symbol means Do practice exam problems (time yourself!) Phys. 102, Review 29, Slide 2

Phys. 102, Review 29, Slide 3 Review lecture ACTs 70% EX2 Some exam problems are inspired by ACTs. 30%

Review homework questions Phys. 102, Review 29, Slide 4 20%! EX2 Some exam problems are inspired by the HW. 100%

Problem solving approaches The not-so-good approaches: Conceptual understanding / reasoning from basic principles: “Reasoning by analogy”/memorization: “I remember every time we’ve done RC circuit problems, V C =  after a long time...” 1.The capacitor is fully charged, so I C = 0 2.Resistor R 3 is in series with C so I 3 = 0 3.But, current can flow around inner loop, so I 1 > 0 4.Algebra! KLR:  – I 1 R 1 – V C = 0, therefore V C <  The good approach: Phys. 102, Review 29, Slide 5 20%! EX2

Problem solving approaches The not-so-good approaches: The “magic” equation: Conceptual understanding / reasoning from basic principles: “What equation will solve this problem? R eq = R 1 +R 2, V = IR?” 1.Redraw the circuit to make it clearer 2.The rightmost resistor is shorted, so no current flows through it! 3.So, the current through the bottom resistor is I 4.Algebra! KLR: E – IR = 0 The good approach: Phys. 102, Review 29, Slide 6 EX2 70%

1. Electricity & circuits Lects. 1 – 9 7

VectorNumber (“scalar”) Property of interacting charges Property of point in space Ex: F E V UEUE [N][J] [N/C]=[V/m] [J/C]=[V] Relationship between F, E, U E, V E points from high to low V Phys. 102, Review 29, Slide 8

WireBattery Circuits & components CapacitorResistor Series and parallel Basic principles: Conservation of charge (KJR) Conservation of energy (KLR) Current In = Current Out Sum of voltages around loop = 0 Phys. 102, Review 29, Slide 9

RC Circuits Phys. 102, Review 29, Slide 10 Charging: Initially the capacitor is uncharged At t = 0 we close switch S 1 After a long time (t =  ): Charge on C builds and saturates Current decreases to zero C acts like a wire C acts like an open circuit + ε ICIC R S1S1 C S2S2 +Q+Q –Q Immediately after (t = 0): No charge on C yet Current I C,0 flows charge onto C Discharging: Initially the capacitor is fully charged At t = 0 we close switch S 2 Immediately after (t = 0): C still fully charged Current I C,0 flows charge off of C After a long time (t =  ): Charge dissipates to zero Current decreases to zero C acts like a battery C acts like an open circuit

2. Magnetism Lects. 10 – 15 11

I Type I: RHR for forces on moving charges and currents Type II: RHR for magnetic fields generated by currents I I Thumb along I Curl fingers along Curl fingers along I Thumb along B field from wire B field inside loop Thumb along Fingers along on + q is out of palm on – q is into palm + q OR: I – q Moving + charges and currentsMoving – charges Thumb along Fingers along II Thumb along I Curl fingers along Magnetism summary Phys. 102, Review 29, Slide 12

1.Is  increasing, decreasing, or constant? 2. If  increases: ε induces B field opposite external B field 3. Type II RHR gives current direction B ind Induced EMF ε opposes change in flux  Side viewTop view B ind B ext If  decreases: ε induces B field along external B field Top view B ext B ind B ext Side view If  is constant: ε is zero, no induced B field I I Curl fingers along I Thumb along B ind B ind I I I I Lenz law Phys. 102, Review 29, Slide 13

2.Magnetic field B Since, 3 things can change  Faraday’s law: “Induced EMF” = rate of change of magnetic flux 1.Area of loop3.Angle φ v t B(t)B(t) B n ω B Faraday’s law Phys. 102, Review 29, Slide 14

3. Light & optics Lects. 16 – 23 15

Light summary Properties of electromagnetic waves Relation between E, B, f, λ Energy density, power & intensity Polarization Ray model of light Reflection Refraction Mirrors Lenses (alone, in combination) The eye (nearsightedness, farsightedness) Interference Constructive and destructive interference Diffraction & resolution Phys. 102, Review 29, Slide 16

Light as a wave (again) Interference: phase shift & path length difference θθ d θ Constructive: phase shift of mλ Destructive: phase shift of (m + ½)λ Phase shift Two & multiple slit maxima Two slit minima Single slit minima Circular aperture minimum Phys. 102, Review 29, Slide 17

Example: Interference Phys. 102, Review 29, Slide 18 Extra practice

4. Modern physics Lects. 23 – 28 19

Quantum mechanics Wave-particle duality Matter waves – particle as a wave (de Broglie) Photons – light as a particle (photoelectric effect) Bohr model quantized orbits & energies, electronic transitions Nuclear & particle physics structure of nucleus & nucleons decay processes (α, β, γ) & rates, binding energy quark model Quantum model quantum numbers (n, ℓ, m ℓ, m s ), Pauli exclusion principle, magnetic properties of atoms Phys. 102, Review 29, Slide 20

Example: wave-particle duality Phys. 102, Review 29, Slide 21 Extra practice

Example: quantum numbers Extra practice Phys. 102, Review 29, Slide 22

Example: quantum atom Extra practice Phys. 102, Review 29, Slide 23

Example: nuclear decay Extra practice Phys. 102, Review 29, Slide 24