phy 2049: physics ii tutoring center is open in room npb 1215, m-f 12:00am -4:00pm. it is free. the...
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PHY 2049: Physics II
Tutoring Center is open in room NPB 1215, M-F 12:00AM -4:00PM. It is free.
The following hitt numbers need to register. Please do so ASAP.
402407 405767 416479 402614 406876 417029 432808 411209 420713 432798
Ch. 31 Electromagnetic Oscillations
RC, RL, LC circuits Driven damped Oscillations Resonance Series RLC circuits Power Transformer
Last time
LC circuit Analogous to a
pendulum L m q x C 1/k
Be careful with ωt in radians (not degrees)
C
q
C
qLiU
LCtqq
C
q
dt
qdL
o
ooo
22
1
2
1
1sin
0
222
2
2
Alternating Currents
A resistance
0
)sin(sin
0sin
tItR
VI
IRtV
R
o
The current and voltage are in phase
Capacitor: AC response
CX
tX
V
tItCVdt
dqti
tCVq
C
C
Co
o
1
)90sin(
)90sin(cos)(
sin
0
The current leads the voltage
Inductor: AC response
The current lags the voltage
LX
tX
Vt
L
Vti
tVdt
diLv
L
L
oo
oL
)90sin(cos)(
sin
HITT
A capacitor in an LC oscillator has a maximum potential difference of 15V and a maximum energy of 360 μJ. At a certain instant the energy in the capacitor is 40 μJ. At that instant what is the potential difference across the capacitor?
A. zero B. 5V C. 10V D. 15VE. 20V
An LC circuit has a capacitance of 30 μF and an inductance of 15mH. At time t = 0 the charge on the capacitor is 10 μC and the current is 20mA. The maximum charge on the capacitor is:
A. 8.9 μC B. 10 μC C. 12 μC D. 17 μC E. 24 μC
A different problem
Yet different A 45-mH inductor is connected to a source of
sinusoidal emf with a frequency of 400 Hz and a maximum emf of 20V. The maximum current is:
A. 0 B. 0.18A C. 1.1A D. 360A E. 2300A ans: B