exam2 (1)

Exam #77777 Exam #77777 Instructor: Profs. Hershfield and Takano PHYSICS DEPARTMENT PHY 2049 Exam 2 April 5, 2022 Name (print, last first): Signature: On my honor, I have neither given nor received unauthorized aid on this examination. TA: Discussion period and day: BEFORE YOU START (1) Print and sign your name on this QUESTION sheet (in the space provided above). (2) Your TEST NUMBER is the 5-digit number at the top of this QUESTION SHEET. (3) Code your 5-digit test number onto lines 76 - 80 of your ANSWER SHEET (scan sheet). (4) Code your name and UFID on your ANSWER SHEET. (5) For each question, blacken the circle of your intended answer completely on the answer sheet. DARKEN CIRCLES COMPLETELY, using a No. 2 pencil or blue or black ink. Do not make any stray marks on the answer sheet. (6) You can do scratch work on this question sheet. Additional scratch paper is available if you want it. (7) For each question, choose the best answer. Many answers are rounded. Choose the most correct answer. Use g = 9 . 80 m/s 2 . All questions carry equal credit. There is no penalty for guessing. (8) You may use a simple electronic calculator - not a cell phone. No books, notes, or other resources are permitted. (9) You may separate the included formula sheets and question pages if you wish. There is no need to reattach or staple them later. WHEN YOU FINISH (1) Check that you have coded your name, UFID and test number on your answer sheet (scan sheet). Check that your name and signature are on this question sheet. (2) Turn in your answer sheet (scan sheet) AND question sheet. Please keep your scratch paper. (3) No credit will be given unless you turn in both the answer sheet and the question sheet with your name on each.

Exam #77777 Exam #77777 Capacitors: RC circuit: Inductors: RL circuit: LC circuit: RLC circuit: (not driven) Resistors: Current: Constants: 𝑒 = 1.6 × 10 −19 C Formulas kilo (k) = 10 3 ; centi (c) = 0.01; milli (m) = 10 -3 ; micro (μ) = 10 -6 ; nano (n) = 10 -9 ; pico (p) = 10 -12 Inductors add in series and parallel with the same rules as resistors. (charging) (discharging) E .

Exam #77777 Exam #77777 1. In the figure, E = 6 V, R 1 = R 2 = R 3 = 100 Ω, and C = 50 μ F. The capacitor is initially uncharged. What is the current through resistor R 2 instantaneously after switch S is closed, in mA? (1) 20 (2) 16 (3) 12 (4) 8 (5) 4 2. In the figure, all resistances are 10 Ω, and R 3 dissipates a power of 0.1 W. What is the emf of the battery, in volts? (1) 4.0 (2) 5.0 (3) 3.0 (4) 2.0 (5) 1.0 3. In the figure, E 1 = 6 . 0 V, E 2 = 3 . 0 V, and all resistances are 10 Ω. What is the electrical potential difference, in volts, across resistor R 4 ? (1) 3.0 (2) 2.5 (3) 3.5 (4) 4.0 (5) 2.0 4. In the figure, R 1 = 200 kΩ, R 2 = 400 kΩ, and the emf of the battery is 10 V. A voltmeter, whose internal resistance is 1.0 MΩ, is used to measure the voltage across R 2 . How much will the measured voltage deviate from the true voltage? (1) By 12%. (2) By 9%. (3) By 7%. (4) By 5%. (5) By 2%. 5. Two particles with the same mass and charge move clockwise in a constant magnetic field, but with different radii as shown in the figure. Which of the following is true of the velocities and periods for the two particles? x x x x x x x x x x x x x x x x x x x x x x x x 1 2 (1) v 1 < v 2 and T 1 = T 2 (2) v 1 > v 2 and T 1 = T 2 (3) v 1 < v 2 and T 1 < T 2 (4) v 1 < v 2 and T 1 > T 2 (5) v 1 > v 2 and T 1 < T 2 6. An electron moving with velocity 2 × 10 6 m/s ˆ i enters a region of uniform electric field ~ E = - 4 × 10 6 V/m ˆ j . What magnetic field will produce a force that cancels the electric force, resulting on zero net force on the electron? (1) - 2 T ˆ k (2) 2 T ˆ k (3) 0 . 5 T ˆ k (4) - 0 . 5 T ˆ k (5) - 8 T ˆ k

Exam #77777 Exam #77777 7. A square loop of wire of side 2 cm with current i = 6 A is partially in a uniform magnetic field of 5 T going into the page as shown in the figure. What is the net force on the loop? x x x x x x x x x x x x x x x x x x x x i x y (1) - 0 . 6 N ˆ j (2) +0.6 N ˆ j (3) +1.2 N ˆ j (4) - 1 . 2 N ˆ j (5) 0.6 N ˆ i 8. In the figure a current carrying loop of wire is in a magnetic field. The direction of the current flow and the direction of the magnetic field are shown in the figure. What is the direction of magnetic moment of the loop and the direction of torque on the loop? Here, “up” means towards the top of the page, and “down” means toward the bottom of the page. The torque direction is either clockwise or counterclockwise relative to the axis of rotation. (1) down and counterclockwise (2) up and counterclockwise (3) down and clockwise (4) up and clockwise (5) right and clockwise 9. Four wires have currents flowing perpendicular to the page with the directions shown in the figure. The magnitudes of the currents are i 1 = 4 A and i 2 = i 3 = i 4 = 2 A. If d = 5 cm, what is the magnitude of the magnetic field at the origin? x 4 1 3 d 2 d d d (1) 18 μ T (2) 32 μ T (3) 40 μ T (4) 16 μ T (5) 24 μ T 10. In the figure a square loop of side 2 cm carries current i 1 = 25 A. It is placed next to a long wire with current i 2 = 15 A with the closest segment being 1 cm from the long wire. What is the net force on the loop? 1cm i 2 i 1 (1) 1 . 0 × 10 - 4 N (2) 2 . 0 × 10 - 4 N (3) 0 . 5 × 10 - 4 N (4) 1 . 5 × 10 - 4 N (5) 2 . 5 × 10 - 4 N 11. A circular loop of radius r = 2 cm carries current 1 A. As shown in the figure it is placed next to a long wire carrying current 3 A. What is the magnitude and direction of the magnetic field at the center of the loop? r r (1) 1 . 6 × 10 - 5 T into page (2) 1 . 6 × 10 - 5 T out of page (3) 4 . 6 × 10 - 5 T into page (4) 4 . 6 × 10 - 5 T out of page (5) 3 . 2 × 10 - 5 T into page

Exam #77777 Exam #77777 19. A 50 mH inductor, in series with a 10 Ω resistor, is connected to a 60 Hz emf source. What is the phase angle by which the current in the circuit lags behind the emf of the source? (1) 62 ◦ (2) 90 ◦ (3) 73 ◦ (4) 107 ◦ (5) 51 ◦ 20. A series RLC circuit, driven by a 60 Hz emf source with a fixed amplitude, consists of a 100 Ω resistor, a 10 mH inductor, and a capacitor whose capacitance can be varied. What is the value of the capacitance, in μ F, that maximizes the power dissipated in the resistor? (1) 700 (2) 570 (3) 430 (4) 290 (5) 120

Scratch paper

Scratch paper