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Unformatted text preview: Dr. Huerta Phy 207 Test 2 ANSWER KEY March 23 2011 Section HJ, MWF 3:35 – 4:25 p. m. Signature: Name: 1 2 3 4 5 ID number: DO THE TWO MULTIPLE CHOICE PROBLEMS [1.] AND [2.] AND DO TWO OUT OF PROBLEMS [3.], [4.], [5.] CROSS OUT THE BOX OF THE PROBLEM YOU WILL NOT DO Your signature signifies that you will obey the HONOR CODE You may be asked to show your photo ID during the exam. PUT AN X NEXT TO YOUR DISCUSSION SECTION: [ ] Dr. Mezincescu 1O, T 9:30 - 10:20 p.m. [ ] Dr. Alvarez 1Q, T 12:30 - 1:20 p.m. [ ] Dr. Huerta 1R, T 2:00 - 2 :50 p.m. You may be asked to show your photo ID during the exam. FORMULAE SHEET e = 1 . 6 × 10- 19 C, m e = 9 . 1 × 10- 31 kg, m p = 1 . 67 × 10- 27 kg, k = 1 4 π = 9 × 10 9 N · m 2 C 2 . Coulomb’s Law, Electric Fields (N/C), Electric Field Flux Φ , and Gauss’ Law ~ F = q 1 q 2 4 π r 2 ~ F q = q ~ E, | ~ E Q | = kQ r 2 , Φ closed surface = H ~ E · d ~ A = q inside Electric Field and sheets of surface charge density σ : On each side of an infinite sheet E n = σ 2 , but outside the surface of a conductor E n = σ . Force, Potential Energy and Torque for an Electric Dipole The Force, torque, and potential energy of an electric dipole ~ p immersed in uniform electric field ~ E are ~ F total = 0 , U =- ~ p · ~ E, ~ τ = ~ p × ~ E. Harmonic Oscillator: F x =- kx , ω = p k/m Electric Potential and Energy : W agent = ( K + U ) f- ( K + U ) i , W field = U i- U f U q ( ~ r ) = qV ( ~ r ) , V i- V f = R f i ~ E · d~s, ~ E =- ~ ∇ V =- ∂V ∂x ˆ ı- ∂V ∂y ˆ - ∂V ∂z ˆ k, E r =- ∂V ∂r Capacitance Q = CV, C = κ o A d , series 1 C eq = 1 C 1 + 1 C 2 , parallel C eq = C 1 + C 2 Circuits i = R ~ J · ˆ ndA, ~ J = q + n + v D + + q- n- v D- = σ ~ E, σ = 1 /ρ, V = iR, R = ρL/A Resistors : in series R eq = R 1 + R 2 , in parallel 1 R eq = 1 R 1 + 1 R 2 Kirchhoff’s rules : (1) at a junction, current in equals current out, (2) sum of voltage rises around a loop equals zero. RC Circuits: E , switch, R , and C in series, switch closes at t = 0, q ( t ) = C E 1- exp (- t/RC ) + q ( t = 0) exp (- t/RC ) , i ( t ) = dq dt ....
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- Fall '11
- Energy, Electric charge, Dr. Huerta, Dr. Huerta 1R