PHYS 211 Exam 2, Spring 2014

1A charged particle (mass = 4.0 xp, charge = 5.0 C) moves ina region where the only force on it is magnetic. What is the magnitude of the acceleration of the particle at a point where the speed of the particle is §.0 kin/s, the magnitude of the magnetic field is 8.0 mT, and the angle between the direction of the magnetic field and the velocity of the particle is 60°? A) a8km/s> BY 2Ski/s?— CC) 39 km/s’) 52 kinds? (8 km/s? 2. Asquare loop (= 0.20 m) consists of 50 closely wrapped turns, each carrying a current of 0.50 A. The loop is oriented as shown in a uniform magnetic field of 0.40 T directed in the positive y direction. What is the magnitude of the torque on the loop? A) 0.12N-m B) 0.21N-m C) 1.73N-m (D))035N-m E) 0.20N-m “3_/ An electron follows a circular path (radius = 15 cm) in a uniform magnetic field (magnitude = 3.0 Y G). What is the period of this motion? A) 0.18 us B)\0.12 ps C) 1.2ms D) 1.8ms E) 1.8 ps _—_—_— ——$—— 4. What is the magnitude of the magnetic field at point P if a= R and b = 2R? C) Aol 3p! (Pret 12R 16R TER April 25, 2014 Quiz2 Phys 211 5:00 p.m. 5, Gauss's Law states that the net electric flux, fr -dA, through any closed surface is proportional q , be to the charge enclosed: fre dA = =: The analogous formula for magnetic fields is: 6) fBdA=0. &— 6. Two solenoids are each made of 2 000 turns of copper wire per meter. Solenoid I is 2 m long, while solenoid II is 1 m long. When equal currents are present in the two solenoids, the ratio of J the magnetic field B, along the axis of solenoid I to the magnetic field By along the axis of solenoid II, By/Bu. is Be Me (A) wm? B) 4. C) 1/4. D) 1/2. (I. /7. A5-turn square loop (10 cm along a side, resistance = 4.0 Q) is placed in a magnetic field that makes an angle of 30° with the plane of the loop. The magnitude of this field varies with time according to B = 0.50, where ¢ is measured in s and B in T. What is the induced current in the coil at f= 4.0 s? A) 5.0mA B) 13mA C) 25mA B® mA E) SOmA (9 A rod (length = 10 cm) moves on two horizontal frictionless conducting rails, as shown. The magnetic field in the region is directed perpendicularly to the plane of the rails and is uniform and constant. If a constant force of 0.60 N moves the bar at a constant velocity of 2.0 m/s, what is the current through the 12-Q load resistor? A) 034A Pps A C) 0.39A D) 0.43 A E) 0.37A 9) A long solenoid has a radius of 2.0 cm and has 700 turns/m. If the current in the solenoid is decreasing at the rate of 8.0 A/s, what is the magnitude of the induced electric field at a point 2.5 cm from the axis of the solenoid? A) 88 uV/m B) 44 uV/m & 56 wV/m D) 8.8 uV/m E) 69 uV/m Page 3 of 4 Dw 2A _—_—— es {}-———-wv Vv xa 6.s A) 600 A/s B) 500 A/ €))2 s €)) 200 A/s D) 800 A/s E) 400 A/s li. The switch in the figure is closed at = 0 when the current / is zero. When J = 15 mA, what is the potential difference across the inductor? A) 0 B) 190V C) 240V (0) jsov E) 60V 12. A-series LC circuit contains a 100 mH inductor, a 36.0 mF capacitor and a 12 V battery. The frequency of the electromagnetic oscillations in the circuit is A) 44.0 Hz. B) 5.73 x 107 Hz. (3 ) 2.65 Hz. ) 0.442 Hz. E) 9.55 x 10° Hz.