All answers have been checked against the answer key, and should be presumed to be correct. You should ask for help in the recitations if you are unable to obtain these results.
62. 69.2 Hz
68. (a) 6.4%, (b) 98.5%
These answers neglect a relative phase in the total current, which causes
the amplitude of the total current through the resistor and capacitor to be
slightly less than the sum of the amplitudes of the current through the
resistor and the capacitor. This is similar to the situation discussed for
voltages in section 13, which we skipped. In fact, since the impedence
through one branch is much greater than through the other in either part
of the question, the phase of the total current is close to the phase of the
current through the branch with the least impedence. So to a reasonable
approximation, you really do not have to consider the phases in this question.
The rest of the Chapter 21 answers can be found in the Chapter 21 page.
26. We skipped section 13, so you can skip this question.
27. This is also on section 13, so you can skip it.
28. The stored energy oscillates back and forth between the resistor and capacitor.
29. In a spring, energy oscillates back and forth between kinetic energy and potential energy. The potential energy is kx2/2, and the kinetic energy is mv2/2. In the LC system, energy oscillates between the energy of the stored charge in electric field in the capacitor, Q2/(2C), and the energy stored in the magnetic field in the inductor, LI2/2. Taking Q as the analog of the position x of the mass on the spring, its time variation v is the analog of the current I. Then k is analogous to 1/C and m is analogous to L. This implies that the inductance plays the role of inertia, which is appropriate since it resists change in the current in much the same way that mass resists change in the velocity in mechanics.
The rest of the Chapter 21 answers can be found in the Chapter 21 page.
| Physics 222 | Department of Physics | University of Tennessee |