25.Induced E-fields.Consider an electrostatic electric fieldE1and an induced electric fieldE2. Which of the following correctly describe/s these fields?I. Both fields are derivable from electric potentials.II.E1is produced by a static charge distribution, whileE2is induced by a changing mag-netic field.III. Each field exerts a forceFi(i= 1,2)of the formFi=qEion a chargeq.A. I onlyB. III onlyC. II and III onlyD. I, II, and IIISolution:II and III only26.maxiD.Consider a charging parallel plate capacitor. Its plates have areaAand separationdistanced. What is the maximum displacement current if the electric field between theplates varies according toE(t) =E0sin(ωt)?A – 11
Second Long ExamFirst Semester, AY 2014–2015Physics 7227.oh-EM-F!A short air-core cylindrical inductor coil has self-inductanceL= 400μH. Thecurrentiin this inductor increases uniformly from 0 to16 Ain4.0μs. What is the magni-tude and direction of the self-induced emf?28.induc-THOR.A flat spiral air-core inductor coil has self-inductanceL= 40μH. Thecurrentiin this inductor decreases uniformly from8.0 Ato4.0 Ain2.0μs. What is themagnitude and direction of the self-induced emf?29.LC ka?A1 mFcapacitor is charged by connecting to a10 Vdc power supply.Thecapacitor is disconnected to the power supply and then connected across an inductor. Theangular frequency of the oscillation is5×102rad/s. What is themaximumcurrent in thecircuit?A.5 AB.10 AC.5×10-2AD.5×106ASolution:i=-wQsin(wt)30.Magneto’s Coil.Magneto’s coil has a self-inductance of50μHand a resistance of5.0 Ω.It is connected to a10 Videalbattery. What is the total magnetic energy stored in his coilwhen the steady-state current is reached?A – 12
Second Long ExamFirst Semester, AY 2014–2015Physics 722
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