Phys 102 Lect 29 Final exam review 1

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

Review lecture ACTs Some exam problems are inspired by ACTs. EX 2 30% 70% Phys. 102, Review 29, Slide 3

Review homework questions Some exam problems are inspired by the HW. EX 2 20%! 100% Phys. 102, Review 29, Slide 4

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

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

1. Electricity & circuits Lects. 1 – 9 7

Relationship between F, E, UE, V F Number (“scalar”) UE [N] Ex: [J] Ex: po Pro in per t i ty n sp of ac e in te Pro ra pe ct r in ty gc o ha f rg es Vector E Ex: V [N/C]=[V/m] E points from high to low V [J/C]=[V] Ex: Phys. 102, Review 29, Slide 8

Circuits & components Wire Battery Series and parallel Capacitor Resistor Basic principles: Conservation of charge (KJR) Conservation of energy (KLR) 1 1 2 2 Current In = Current Out Sum of voltages around loop = 0 Phys. 102, Review 29, Slide 9

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

2. Magnetism Lects. 10 – 15 11

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

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

Faraday’s law: “Induced EMF” = rate of change of magnetic flux , 3 things can change Since 1. Area of loop 2. Magnetic field B 3. Angle φ B(t) v B +1. 0 ω +0. 5 0 0 10 20 n B t -0. 5 -1. 0 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 Phase shift Constructive: phase shift of mλ Destructive: phase shift of (m + ½)λ θ d θ θ Two & multiple slit maxima Two slit minima Single slit minima Circular aperture minimum Phys. 102, Review 29, Slide 17

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

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 Quantum model quantum numbers (n, ℓ, ms), Pauli exclusion principle, magnetic properties of atoms Nuclear & particle physics structure of nucleus & nucleons decay processes (α, β, γ) & rates, binding energy quark model Phys. 102, Review 29, Slide 20

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

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