ECE 252 Introduction to Electrical Engineering
Lesson 7. Inductors and Capacitors and Their Uses Homework
Version S16
Homework partner name: _______________________Homework partner name: ________________________
1. Quickies
a) Inductors frequently have cores made of __________________ to increase the inductance by concentrating
the field.
b) Name a device that depends on the magnetic field created by an inductor to function.
_________________________________________
c) The units of inductance are _______________.
d) A 20 µF capacitor has a charge of 100 µC. Its voltage is __________________ V.
e) You can’t instantaneously change the _____________________ across a capacitor.
f) All of the energy contained in a 6.25 H inductor carrying .02 A is transferred to an initially uncharged 100 µF
capacitor. The voltage on the capacitor will become _________________ V.
Signatures: ________________________________________________________________________
2. Completely label the diagram. Use device equations (one for each passive device) and Kirchhoff’s Laws to
write equations to solve for the voltage across and the current through each circuit element. Do not solve.
Signatures: ________________________________________________________________________
3. v(t) = 6 + 4e-700t volts, L = 30 mH, C = 20 µF, R = 250 Ω. The downward current in the inductor is 0.5 A at t =
0. Label the diagram. Find the magnitude and direction of the current flowing in each of the four elements as a
function of time. Simplify the results. Note: Don’t forget about the initial conditions or the lower limit on the
integral.
Signatures: ________________________________________________________________________
4. Given an unknown capacitor with a capacitance somewhere between 10 µF and 100 µF, a 1 M Ω resistor, a
multimeter, a 1.5 V battery, a toggle switch, and a stopwatch, describe an experiment to determine the capacitance
of the unknown capacitor.
Signatures: ________________________________________________________________________
BONUS (No partial credit.) A hominid bone is found at an ancient dig site. The ratio of its carbon-14 to carbon12 is found to be 8% of the ratio that is found in a comparable modern bone. How old is the ancient bone? Show
your calculations. Note: Carbon-14 has a half-life of 5730 years. It is possible to make these calculations based
on what you know about the exponential decay of radioactive material. Using the Internet is not necessary.
Signatures: ________________________________________________________________________