Download Name: Magnetic Materials – Practice 1. In an oscillating LC circuit

Name: _______________________________
Magnetic Materials – Practice
1. In an oscillating LC circuit with L = 50 mH and C = 4.0 μF, the current is initially a maximum.
How long will it take before the capacitor is fully charged for the first time?
2. LC oscillators have been used in circuits connected to loudspeakers to create some of the
sounds of electronic music. What inductance must be used with a 6.7 μF capacitor to produce
a frequency of 10 kHz, which is near the middle of the audible range of frequencies?
3. A square loop of wire has sides of length 2.0 cm. A magnetic field is directed out of the
page and its magnitude is given by B = 4.0t2y, where B is in teslas, t is in seconds, and y is in
meters. At t = 2.5 s, what are the magnitude and direction of the emf induced in the loop?
4. A coil is connected in series with a 10.0 k resistor. An ideal 50.0 V battery is applied
across the two devices, and the current reaches a value of 2.00 mA after 5.00 ms.
A. Find the inductance of the coil.
B. How much energy is stored in the coil at this same moment?
5. At t = 0, a battery is connected to a series arrangement of a resistor and an inductor. If
the inductive time constant is 37.0 ms, at what time is the rate at which energy is dissipated
in the resistor equal to the rate at which energy is stored in the inductor's magnetic field?
1 2
t
d
(
LI )

d UB

L

2
[Hint: Set PThermal =
 I 2R =
where I = (1  e L ) and  L  ]
R
R
dt
dt
Solutions:
1. 7.0 x 10-4 s
4. A. 97.9 H B. 1.96 x 10-4 J
2. 3.8 x 10-5 H
5. 2.56 x 10-2 s
3. 8.0 x 10-5 V, CW