Injuiced meh a rectangular coil with area 1 m 2 is

21. Injuiced mEh! A rectangular coil with area 1 m
2
is located in a region of uniform magnetic field that
varies with time according to B ( t ) = (1
T
/
s 2
) t 2 . The
magnetic field is at an angle of 60
◦
with respect to the
plane of the coil as shown. What is the magnitude of
the induced emf in the coil at time t = 1 s?
A. 2 V
B.
√
3 V
C. 1 V
D.
√
3 / 2 V
For the next two items, consider a metal rod with
length L = 1 m forced to move with constant speed
v = 1
m
/
s
along two parallel metal rails that are con-
nected to a resistor R = 3 Ω . The circuit is immersed
in a uniform magnetic field B = 2 T directed out of
the page as shown.
22. Emotional. What is the motional emf in this circuit?
A – 7

23. Injuiced Ay! What is the direction of the induced current through the resistor ?
24. Plot-teaus. A time-varying current, whose plot is shown, is allowed to flow through
an inductor L . Which of the following choices correctly shows the total magnetic
field energy stored in the inductor as a function of time?
For the next two items, consider the circuit shown.
The capacitor is initially charged to Q
0
. The switch
is then flipped from 1 to 2 to form an LC circuit. The
angular frequency is taken to be ω .
25. Charge. If the stored charge in the capacitor decreases to half its initial value, what
is the magnitude of the current passing through the inductor at that instant?
A.
1
2
ωQ
0
B. C.
D. ωQ
0
√
2
2
ωQ
0
√
3
2
ωQ
0
A – 8

Second Long Exam First Semester, AY 2015–2016 Physics 72
26. Time. What time will the magnitude of the current through the inductor reach half
its maximum value at the first instance?
27. Q(t)p2t. Consider the following figure for an underdamped LRC circuit. What
functions best describe the dashed lines? Take a > 0.
28. Mutually Assured. Two identical coils situated near each other have a mutual
inductance of 3 H. A steady current of 5 A linearly decreases to zero in a span of
1 second. What is the average induced EMF in the second coil during the whole
duration?
29. Too much! Consider an LRC circuit with a 1 . 0-Ω resistor. Which of the following
values of inductance and capacitance will result to overdamping?
A. L = 4 . 0 μ H, C = 1 . 0 μ F
B. L = 1 . 0 μ H, C = 0 . 5 μ F
C. L = 0 . 5 μ H, C = 4 . 0 μ F
D. L = 0 . 25 μ H, C = 0 . 25 μ F
A – 9

Second Long Exam First Semester, AY 2015–2016 Physics 72
30. Arrow. Consider the phasor diagram for an LRC
series circuit connected to an AC source as shown.
Which of the following best describes the voltages
across each element in the circuit if the current has
amplitude I ?