*6
Determine the Concept The magnetic energy stored in an inductor is given by
U m = 1 LI 2 . Doubling I quadruples Um. (c) is correct.
2
9
(a) False. The induced emf in a circuit is proportional to the rate of change of the
magnetic flux through the cir
*1
Determine the Concept We know that the magnetic flux (in this case the magnetic field
because the area of the conducting loop is constant and its orientation is fixed) must be
changing so the only issues are whether the field is increasing or decreasin
4
Determine the Concept Applying the right-hand rule to the wire to the left we see that
the magnetic field due to its current is out of the page at the midpoint. Applying the righthand rule to the wire to the right we see that the magnetic field due to i
19
Determine the Concept If we apply Kirchhoffs loop rule with the switch closed, we
obtain IR VC = 0. Immediately after the switch is closed, I = 0 and we have = VC.
(b) is correct.
20
Determine the Concept The energy stored in the fully charged capaci
71
Picture the Problem We can model this system as two capacitors in series, C1 of
thickness d/4 and C2 of thickness 3d/4 and use the equation for the equivalent capacitance
of two capacitors connected in series.
Express the equivalent capacitance
of the
4
Picture the Problem The energy stored in the electric field of a parallel-plate capacitor is
related to the potential difference across the capacitor by U = 1 QV .
2
Relate the potential energy stored in
the electric field of the capacitor to the
potent
2
Picture the Problem A charged particle placed in an electric field experiences an
accelerating force that does work on the particle. From the work-kinetic energy theorem
we know that the work done on the particle by the net force changes its kinetic ene
PHYS 272
Solutions to HOMEWORK 2
7
Determine the Concept The negative point charge at the center of the conducting shell
induces a charge +Q on the inner surface of the shell. (a ) is correct.
22
Picture the Problem The electric field on the axis of a di
PHYS 272
Solutions to HOMEWORK 1
3
Determine the Concept During this sequence of events, negative charges are attracted
from ground to the rectangular metal plate B. When S is opened, these charges are trapped
on B and remain there when the charged body i
November 25, 2008
Physics 272 Exam 3:
Name: (E Q >4'W
The value of the elecnic constant eo=8.85 x1012 C2/Nm2 .
The value of the magnetic constant uo= 4 1: x10 T m/Az
Solve the ve questions in the exam.
1.-
, i. At the instant them charged body is at th
Consider two capacitors, each having plate sepa-
ration a. In each case, a slab of metal of thick-
ness d/3 is inserted between the plates. In case
(a), the slab is not connected to either plate. In
case (b), it is connected to the upper plate. The
capaci
Consider the pairs of phasors below, each shown
at t = 0. All are characterized by a common fre-
quency of oscillation w. If we add the two oscil-
lations together, the maximum amplitude of the
phasors is achieved for pair
@@@@@
/N {N W), /% WK
\/ jkj Kj
*1
Determine the Concept Because the rms current through the resistor is given by
I rms = rms R and both rms and R are independent of frequency, (b) is correct.
33
Picture the Problem We can use T = 2/ and = 1
LC to relate T (and hence f) to
L and C.
2