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# Problems

Author: E.E. Kimberly

 Problem Answer 1 In the diagram, a cross-section of a conductor is shown moving to the right in a magnetic field. Will the emf generated in the conductor be toward or away from the observer? 2 If the magnetic field of Problem 1 be of a uniform strength of 10,000 lines per sq cm, the immersed perpendicular length of conductor therein be 10 cm, and the velocity of motion of the conductor perpendicular to the field be 100 ft per sec, what is the magnitude of the generated emf? 3.05 volts 3 Show the flux in the magnetic circuit of the four-pole generator of Fig. 10-13. Indicate the directions of the lines of flux with arrowheads. 4 An electric heater whose resistance is 60 ohms is connected to a 115-volt circuit. How much current flows in the heater? 5 A magnetic field links a 1-turn coil or one turn of wire and varies in magnitude at the rate of 8109 lines of flux per second. Calculate the generated voltage. 6 If the coil of wire in Problem 5 contained 10 turns in series, what would be the generated voltage? 7 If in Fig. 2-2 (a) the total flux is 1.27108 lines and it is uniformly distributed, what would be the maximum value of the sinusoidal voltage generated in a conductor rotating 1 revolution per sec? 4 volts 8 A conductor 10 cm long is caused to move across a field of 80,000 lines per sq in., as in Fig. 2-1 (a), at a velocity of 100 ft per sec. Find the emf generated between the ends of the conductor. 9 Calculate the maximum emf generated in a 20-turn coil rotating on its axis 200 revolutions per sec. The maximum flux enclosed in the loop is 400,000 lines. 10 A coil of 100 turns is cut by a magnetic field which is rising at a rate of 1 million lines per minute. Calculate the emf generated. 1/60 volt 11 When at working temperature the heating element of an electric smoothing iron has a resistance of 12 ohms. How much current will it draw from a 115-volt line? 12 A conductor 4 in. long is caused to oscillate linearly with sinusoidal velocity across a magnetic field whose strength is 80,000 lines per sq in. The amplitude of oscillation is 4 in. Calculate the maximum voltage generated in the conductor when its frequency of oscillation is 20 cycles per sec.

Last Update: 2011-02-23