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77777 77777 Instructor(s): H. Monkhorst PHYSICS DEPARTMENT PHY 2005 Exam 2 Name (print, last first): February 16, 2005 Signature: On my honor, I have neither given nor received unauthorized aid on this examination. YOUR TEST NUMBER IS THE 5-DIGIT NUMBER AT THE TOP OF EACH PAGE. (1) Code your test number on your answer sheet (use 76–80 for the 5-digit number). Code your name on your answer sheet. DARKEN CIRCLES COMPLETELY. Code your UFID number on your answer sheet. (2) Print your name on this sheet and sign it also. (3) Do all scratch work anywhere on this exam that you like. Circle your answers on the test form. At the end of the test, this exam printout is to be turned in. No credit will be given without both answer sheet and printout with scratch work most questions demand. (4) Blacken the circle of your intended answer completely, using a #2 pencil or blue or black ink. Do not make any stray marks or some answers may be counted as incorrect. (5) The answers are rounded off. Choose the closest to exact. There is no penalty for guessing. (6) Hand in the answer sheet separately. Physical Constants: e = 1.6 × 10−19 C µ0 = 4π × 10−7 T·m/A 1. A potassium ion (q = e, m = 39 × 1.67 × 10−27 kg) is moving with a speed of 5 × 105 m/s, perpendicular to a magnetic field. What must be the magnitude of the field if the particle is to follow a circle with 25-cm radius (in Tesla)? (1) 0.81 (2) 81.0 (3) 22.0 (4) −81.0 (5) not enough information 2. A long solenoid is wound on a wooden rod. I has 6,000 loops on its 50-cm length. How large is the magnetic field in the solenoid if the current of 3 A flows through it (in Tesla)? (1) 4.52 × 10−2 (2) 4.52 (3) 2.26 (4) 2.26 × 10−2 (5) 0.00 3. A certain meter movement has a resistance of 50Ω. It deflects full scale for a current of 0.0100 A. How large a shunt resistance is needed to make this into a 1.0 ammeter (in Ω)? (1) 0.51 (2) 51.0 (3) 5.1 (4) 5.1 × 10−3 (5) 25.0 4. The Earth’s magnetic field in Oklahoma has an average value of 0.62 × 10−4 T. It is directed at an angle of 71◦ below the horizontal. Find the flux through a circular coil (r = 25cm) lying on a table (in Weber). (1) 1.15 × 10−5 (2) 0.115 (3) 3.96 × 10−5 (4) 0.0 (5) −1.15 × 10−5 5. Two coils are wound on a bar of iron. The secondary coil has 650 loops of wire on it. Each loop has a radius of 0.50 cm. As the switch is turned on in the primary, the magnetic field increases from 0 to 0.75 T in 0.40 s. Find the average emf induced in the secondary during this time (in V). (1) 9.6 × 10−2 (2) 96.0 (3) 960.0 (4) 480.0 (5) 3.06 × 10−2 6. What is the potential difference (in V) between the ends of a 80-cm long straight wire that is moving sideways perpendicular to a magnetic field? The speed is 20 m/s, and the field is B = 0.30 T. (1) 4.8 (2) 4.8 × 10−2 (3) 480 (4) 240 (5) 120 77777 77777 7. A current i = 7 sin(30t) Amperes flows through a 20Ω resistor. How much power is lost in the resistor (in Watts)? (1) 490 (2) 245 (3) 70 (4) 140 (5) 0.0 8. An uncharged 3-µF capacitor is connected with a switch, a 6 × 105 -Ω resistor, and a 12-V battery. Find (a) the current in the circuit just after the switch is closed (in A), and (b) the final charge on the capacitor (in C). (1) (2) (3) (4) (5) (2.0 × 10−5 , (3.6 × 10−5 , (3.6 × 10−3 , (3.6 × 10−5 , (3.6 × 10−2 , 3.6 × 10−5 ) 2.0 × 10−5 ) 2.0 × 10−5 ) 2.0 × 10−3 ) 2.0 × 10−4 )