Lenz Law - General Physics - Past Paper, Exams of Physics

Download Lenz Law - General Physics - Past Paper and more Exams Physics in PDF only on Docsity! St. Vincent College PH 112: General Physics II Exam V 7/28/2005 The exam consists of 4 questions. The questions may not be worth the same number of points, read the entire exam before beginning work. Put your name on all pages. Problem 1 30 Problem 2 30 Problem 3 20 Problem 4 20 Total 100 1. (30 pts) a) (5 pts) A loop of wire is placed in a uniform magnetic field. For what orientation of the loop is the magnetic flux a maximum? b) (5 pts) A thick wire loop is placed around a solenoid, as shown in the figure below. Initially, there is no current flowing in the solenoid. However, when the solenoid is connected to a battery, current starts to flow in the direction indicated by the two arrows. Indicate, on the drawing, the direction in which current is induced in the thick loop of wire around the solenoid. c) (5 pts) Current is initially flowing to the right through the long, straight, thick wire shown in the figure below. Indicate, on the diagram, the direction of the magnetic field produced by this current through the loop of wire containing the resistor. Also indicate the direction of the induced current in the wire loop with the resistor if the current in the thick wire is decreasing. 3. (20 pts) a) (10 pts) Calculate the inductance L in a series RL circuit (like the one we did in class) where R = 0.5 Ω and the current increases to one-fourth its final value in 1.5 s. b) (10 pts) If the RL circuit is connected to a 12 V battery, how much energy is stored in the magnetic field of the inductor at this point in time? 4. (20 pts) An automobile has a vertical radio antenna 1.2 m long. The automobile travels at 65 km/h on a horizontal road where the magnitude of the Earth’s magnetic field is 50 µT directed toward the north and downward at an angle of 65◦ below horizontal. a) (10 pts) In what direction should the automobile be driving in order to generate the maximum motional emf in the antenna, with the top of the antenna positive with respect to the bottom? b) (10 pts) What is the magnitude of the maximum motional emf generated when the automobile moves in the direction you have specified?