|
|
Problems 1025 Section 32.1 Self-Inductance 1. A coil has an inductance of 3.00 mH, and the current in it changes from 0.200 A to 1.50 A in a time of 0.200 s. Find 2. A coiled telephone cord forms a spiral with 70 turns, a diameter of 1.30 cm, and an unstretched length of 60.0 cm. 4. Calculate the magnetic flux through the area enclosed by a 300-turn, 7.20-mH coil when the current in the coil is A 10.0-mH inductor carries a current I " I max sin 1t, with I max " 5.00 A and 1/2) " 60.0 Hz. What is the back emf as a function of time? 6. An emf of 24.0 mV is induced in a 500-turn coil at an 2 . What uniform rate of decrease of current through the 8. The current in a 90.0-mH inductor changes with time as 2 # 6.00t (in SI units). Find the magnitude of the induced emf at (a) t " 1.00 s and (b) t " 4.00 s. (c) At 9. A 40.0-mA current is carried by a uniformly wound air-core solenoid with 450 turns, a 15.0-mm diameter, and 12.0-cm 10. A solenoid has 120 turns uniformly wrapped around a wooden core, which has a diameter of 10.0 mm and a m " 800' 0 . What is the new inductance? 11. A piece of copper wire with thin insulation, 200 m long 7. 5. 3. 12. A toroid has a major radius R and a minor radius r, and is 2 , is essentially the same as the magnetic field of a solenoid that has been bent into a large circle of radius R. (An exact expression of the inductance of a toroid with a L ( ' 0 N 2 A 2)R 1, 2 , 3 = straightforward, intermediate, challenging = full solution available in the Student Solutions Manual and Study Guide = coached solution with hints available at http://www.pse6.com = computer useful in solving problem = paired numerical and symbolic problems P R O B L E M S R Area A r Figure P32.12 13. A self-induced emf in a solenoid of inductance L changes ! " ! 0 e # kt . Find the total charge that passes through the solenoid, assuming the charge is finite. Section 32.2 RL Circuits and the current increases to 90.0% of its final value in 16. Show that I " I 0 e # t/+ is a solution of the differential equation where + " L/R and I 0 is the current at t " 0. 17. Consider the circuit in Figure P32.17, taking ! " 6.00 V, L " 8.00 mH, and R " 4.00 .. (a) What is the inductive IR , L dI dt " 0 15. |