Unit 2:
Capacitors and Inductors in DC Circuits
Recall from your earlier courses that resistance is opposition
to the flow of current. Capacitance, which we'll study in this
unit, is an entirely different electrical property. It's the ability
to store a charge. Capacitors are components that are manufactured
to have this ability.
Inductance, which we'll also study in this unit, is another completely
different electrical property. Inductance is opposition to change in
current, and inductors are
components that are manufactured to oppose changes in current. Suppose
that a circuit with an inductor has a certain current flowing through
it. If you try to increase or decrease that current, then the inductor
will fight against you, and will try to keep the current at its initial
value. Eventually the inductor will lose this fight, and the current
will change, but this will take some time to happen. This is different
from what happens in a circuit with no inductor: if there's no inductor,
then the amount of current can increase or decrease immediately. If
there is an inductor, changes in current take a while to happen.
First, you should read the following sections of Thomas Floyd's Principles
of Electric Circuits (8th edition):
 The Basic Capacitor (Section 121)
 Types of Capacitors (Section 122)
 Series Capacitors (Section 123)
 Parallel Capacitors (Section 124)
 Capacitors in DC Circuits (Section 125)
 The Basic Inductor (Section 131)
 Types of Inductors (Section 132)
 Series and Parallel Inductors (Section 133)
 Inductors in DC Circuits (Section 134)
Then work through the eLesson below.
After you finish the eLesson, you'll be ready to take Quiz #2, perform
Lab #2, and do Homework #2.
Unit 1 Review
 This unit will build on material that you studied in Unit
1. So let's begin by taking this selftest to review what you
learned in that unit.

Capacitance & Capacitors
 Capacitance is a measure of a component's ability to
store charge.
 A capacitor is a device specially designed to have a certain
amount of capacitance.
 This ability to store charge means that capacitors can be dangerous.
Some common electronic devices, such as televisions, contain large
capacitors that can hold a deadly charge long after the device
has been turned off and unplugged. Just
as you should always assume that a firearm is loaded, you should
always assume that a capacitor is charged.
Capacitor Application: A Camera Flash
 A simple, everyday use of capacitors is in the flash unit for a camera.
You need a large charge in a very short time to light up the camera's
flash bulb. The camera's battery cannot provide such a large charge
in such a short time. So the charge from the battery is gradually stored
in a capacitor, and when the capacitor is fully charged, the camera
lets you know that it's ready to take a flash picture.
Schematic Symbol, and Appearance
 Here's the schematic symbol for a standard capacitor:
Often, one of the lines in this symbol is drawn slightly curved, so
that people won't confuse it with the symbol for a voltage source.
 While most resistors look more or less the same, capacitors come
in many different types of package. Here are a few examples of what
they may look like.
ParallelPlate Capacitor
 Most capacitors are parallelplate capacitors, which means that they
consist of two parallel pieces of conducting material separated by
an insulator.
 The insulator between the plates is called the dielectric.
Charging a Capacitor
 When a capacitor is connected across a voltage source, charge flows
between the source and the capacitor's plates until the
voltage across the capacitor is equal to the source voltage.
 In this process, the plate connected to the voltage source's negative
terminal becomes negatively charged, and the other plate becomes positively
charged.


Unit of Capacitance
 Capacitance is abbreviated C.
 The unit of capacitance is the farad, abbreviated F.
 Typical capacitors found in electronic equipment are in the microfarad
(μF) or picofarad (pF) range. Recall that micro means 10^{6} and
that pico means 10^{12}.
 You'll also remember that nano means 10^{9}. But for
some reason, the nanofarad has traditionally not been
used, even in cases where
that might make the most sense.
 For example, if a capacitance is equal
to 1×10^{9} F (or 0.000000001
farads), you might think that you'd write that as 1 nF. But
in fact, most people would write this as either 1000 pF or 0.001 μF.
This is strange and confusing, but you just have to get used to it.
 In recent years, however, it's becoming more common to see nanofarads
(nF) used.
 For instance, the capacitance meters that the EET department
bought 10 or 15 years ago displayed all capacitance values in either μF
or pF. But the capacitance meters that we've bought in the past
5 years display capacitance values in μF, nF, or pF.

Energy Stored by a Capacitor
 Recall from EET 150 that when current flows through a resistance,
energy is dissipated as heat.
 But capacitance does not behave like resistance. A capacitance does
not dissipate energy; rather it stores energy,
which can later be used to do something useful (such as light up a
camera flash) or returned to the circuit.
 The energy W stored by a capacitance C is given
by
W = ½ CV^{ 2}
where V is the voltage across the capacitor. Here energy
(W) is in joules (J), capacitance (C) is in farads (F), and voltage
(V) is in volts (V).
Capacitor Ratings
 Commercially available capacitors have several important specifications:
 nominal value and tolerance
 temperature coefficient
 DC working voltage
 leakage resistance
 Read on for discussion of these specifications.
Nominal Value & Tolerance
 Capacitors are available in a wide range of nominal values, from
1 picofarad to several farads.
 A specific capacitor's actual value is subject to the manufacturer's tolerance
specification. Typical capacitor tolerances range from ±5%
to ±20%.

Capacitor Identification Game
 In lab you'll learn to read the codes on capacitors. You'll
need to become an expert at reading these capacitor codes.
To work on this skill, play the Capacitor
Identification Game.
This
game has a Study mode that reviews the relevant theory, a Practice
mode that lets you practice with no time pressure, and a Challenge
mode that tests your skill while the clock is running.
Temperature Coefficient
 Ideally, a capacitor's capacitance would be the same at all temperatures.
But in reality, capacitance changes as the capacitor gets
warmer or cooler. In many cases, you can ignore this change in capacitance,
but if you need a very precise capacitance value, or if you're
dealing with very large temperature swings, you may not be able to
ignore it.
 A capacitor's temperature coefficient tells you how the capacitance
changes with temperature.
 A positive temperature coefficient means that as the
capacitor's temperature increases, its capacitance also increases.
(And vice versaas the
capacitor's temperature decreases, its capacitance also decreases.)
 A negative temperature coefficient means that
as the capacitor's temperature increases, its capacitance decreases.
(And vice versaas the capacitor's temperature decreases,
its capacitance increases.)
 In addition to telling which way the capacitance changes (increase
or decrease), the temperature coefficient also quantifies the amount
of change. Usually it does this by saying how many parts
per million (ppm) the capacitance changes for each °C change in
the temperature.
 For example, a temperature coefficient of 200 ppm/°C means that
for each °C change in the temperature, the capacitance changes by
0.02%. (That's because 200 ÷ 1,000,000 = 0.0002, which is the
same as 0.02%.)
DC Working Voltage
 The DC working voltage (also called the breakdown
voltage) is the maximum voltage at which a capacitor is
designed to operate continuously.
 Usually, the higher the capacitance value, the lower the DC working
voltage.
 Typical values of DC working voltage are a few volts for very large
capacitors to several thousand volts for small capacitors.
Leakage Resistance
 An ideal capacitor would have infinite resistance, with absolutely
no current flowing between the plates.
 In reality, a capacitor's resistance is finite, resulting in
a small leakage current between the plates.
 Typical values of leakage resistance are 1 MΩ to
100,000 MΩ or more. This is large enough that, from a practical
standpoint, we can often pretend that the resistance is infinite.
Capacitor Types
 Capacitors are often classified by the materials used for the dielectric
(the insulator between the capacitor's plates).
 Some types are air, paper, plastic film, mica, ceramic, electrolyte,
and tantalum.
 Each type has its own advantages and disadvantages; see pages 474478
of the textbook for discussion of the various types.
 Often you can tell a capacitor's type by the appearance of the package.
For example, ceramic capacitors typically look like this:
Here's a typical plasticfilm capacitor:
Here's how electrolytic capacitors usually look:
Electrolytic Capacitors
 Of the different types of capacitors just mentioned, one in particular
deserves special discussion: electrolytic capacitors, which are available
in very large values, up to 100,000 μF and above.
 Unlike most capacitors, they are polarized: one side must remain
positive with respect to the other. Therefore you
must insert them in the proper direction. Inserting them backwards
can result in injury to you or in damage to equipment.
 In this photo of an electrolytic cap, notice that it has little arrows
with negative signs pointing to one end:
The lead that the arrows are pointing to is the negative lead.
 Also, the schematic symbol for an electrolytic cap has a positive
sign to tell you which way to hook up the capacitor:
Variable Capacitors
 Variable capacitors are also available. These contain a knob
or screw that lets you adjust the capacitor's capacitance.
 The schematic symbol has an arrow to show that the component's value
can be adjusted:
Stray Capacitance
 Stray capacitance exists between any two conductors that are
separated by an insulator, such as two wires separated by air. This
means that a circuit may contain some capacitance even if there's no
capacitor in the circuit.
 Stray capacitance is usually small (a few pF), and you can usually
ignore it, but it can have undesirable effects in highfrequency AC
circuits.
Capacitors in Series
Shortcut Rules for Capacitors in Series
Capacitors in Parallel
SeriesParallel Capacitors
 For seriesparallel capacitor circuits, the strategy is very similar
to the strategy that you learned in EET 150 for seriesparallel resistor
circuits:
Combine series capacitors and parallel capacitors to obtain progressively
simpler equivalent circuits, until you've combined all of the capacitors
into a single total capacitance, C_{T}.
 Plenty more practice problems right here:

Don't Connect Capacitors Directly Across a Voltage Source
 In general you should not connect
a capacitor (or combination of capacitors) directly across a voltage source,
since the resulting surge of current could damage the capacitor or the
voltage source:
 Instead, you should always have a resistance in series with the capacitor(s),
to limit the amount of current that flows.
Series RC Network
 A resistor and capacitor connected in series are called a series
RC network.
 Series RC networks have many practical uses. They are often used
in timing circuits to control events that must happen repeatedly at
a fixed time interval.
 One example is a circuit that causes an LED to blink on and
off once every second. There are several ways to design a circuit
to do this, but one of the most common ways uses a series RC circuit. By adjusting the value of the resistor or the capacitor,
the designer can cause the LED to blink faster or slower.
DC RC Circuit
 An RC circuit is any circuit containing, in addition to a
power supply, just resistors and capacitors.
 For now we'll restrict our attention to RC circuits containing DC
voltage sources. We'll refer to such circuits as DC RC circuits.
 Examples: A very simple DC RC circuit just has a resistor,
a capacitor, and a voltage source in series:
 Here's a more complicated DC RC circuit, with several resistors and
capacitors:
Behavior of Capacitors in DC Circuits
Initial, Transient, SteadyState
 In most practical DC RC circuits, the values of current
and voltage change with time as capacitors are charged or discharged.
Typically such circuits contain a switch that is initially open, and
you're interested in the circuit's behavior after the switch
has been closed.
 To remind ourselves of this fact, we often include an open switch
in schematic drawings of DC RC circuits, as in the following picture:
 We distinguish three time periods in the analysis of such DC RC circuits:
 the initial period, when the switch is first closed.
 the transient period, while the capacitors are being
charged or discharged.
 the steadystate period, after the capacitors have been
fully charged or fully discharged.
 As we'll see now, we use different rules to figure out voltages and
currents during these three different time periods.
Initial Currents and Voltages
 The currents and voltages in a circuit at the instant when a switch
is first closed are called the initial currents and initial
voltages.
 In most cases, at this initial instant the circuit's capacitors are
either fully discharged or fully charged. Therefore, using the rules
of thumb you learned above, you'll find the circuit's initial values
of voltage and current by replacing the capacitors either with shorts
(if the capacitors are fully discharged) or with opens (if the capacitors
are fully charged).
SteadyState Currents & Voltages
 When the switch in a DC RC circuit has been closed for a long time,
currents and voltages have reached their steadystate values.
 In most cases, in the steady state the circuit's capacitors are either
fully discharged or fully charged. Therefore, using the rules of thumb
you learned above, you'll find the circuit's steadystate values of
voltage and current by replacing the capacitors either with shorts
(if the capacitors have been fully discharged) or by opens (if the
capacitors have been fully charged.)
Transient Currents and Voltages
 We've just seen how to figure out the initial currents and
voltages in a DC RC circuit and the steadystate currents and
voltages in a DC RC circuit. That covers the instant when
the switch is first closed, and it also covers times a long time later,
after the capacitors have been fully charged or fully discharged.
But what about the inbetween times, after the switch has been closed
but before the capacitors are fully charged or discharged?
 While a capacitor is being charged (or discharged), currents and
voltages change gradually from their initial values to their steadystate
values. We call this the transient period of a DC
RC circuit.
 For instance, consider the simple series RC circuit shown
below:
Here's a graph showing the how current in this circuit changes with
time after the switch is closed. The graph shows current
on the vertical axis and time on the horizontal axis.
 For now, don't worry about the numbers on
the axes. Just look at the shape of the curve. The numbers will be
different if you change the values of V_{S}, R,
or C,
but the curve will always have this shape.
 Notice that the current starts out at its highest value and then
decreases as time passes. But it does not decrease in a straight
line. Instead, the
current decreases very quickly at first, and then decreases more slowly.
 In mathematics, a curve with this shape is called an exponential
curve. So, since the current is decreasing (or decaying) along
a curve of this shape, we call this exponential decay.
 And the graph below shows how the capacitor's voltage changes with
time. Note that this voltage starts at 0 V
and gradually increases until it reaches a maximum when the capacitor
is fully charged. Notice that this curve
has basically the same shape as the other curve, but flipped upside
down. We see again that the voltage changes quickly at first, and
then gradually approaches a final value.
Time Constant
 For any series RC circuit, the quantity R×C is
called the circuit's time
constant. It is represented by the Greek letter τ,
and its units are seconds:
τ = R×C
 The time constant τ is an
indicator of how long the capacitor takes to charge. The larger τ is,
the longer the charge time.
 By the way, the name of Greek letter τ is "tau," which
rhymes with "cow."
How Long to Charge?
 Here is a useful rule of thumb:
For most practical purposes, we may assume that all quantities
in a DC RC circuit have reached their steadystate values after
five time constants.
 So, for example, if we're charging a capacitor in a DC RC circuit,
and if that circuit has a time constant of 1 second, then it will take
about 5 seconds to charge up the capacitor.
 Since one time constant is equal to R×C, we can write
this rule of thumb as an equation:
Time to reach steady state ≈ 5×R×C
 Notice that in this equation I used a "squiggly equals sign" ≈ to
indicate that this is an approximation. Actually, after five time constants
the capacitor will be about 99.3% charged, not completely charged.
For most practical purposes, that's close enough.

 This completes our introduction to capacitors. Now let's turn to
inductors.
Review of Electromagnetism
 Recall that in Unit 1 we briefly considered two related phenomena,
electromagnetism and electromagnetic induction. These two principles
are key to understanding how an inductor operates, so let's do a quick
review.
 In 1820, Hans Oersted discovered that electrical current creates
a magnetic field. This phenomenon is called electromagnetism.
Oersted also realized that the you can increase the strength of the
magnetic field surrounding a currentcarrying wire by winding the
wire into a series of closely spaced loops. A wire that is looped
in this way is called a coil.
 A few years later, Faraday discovered that a voltage is induced
in a wire whenever there's a change in the size of the magnetic field
surrounding the wire. This phenomenon is called electromagnetic
induction. Also, the induced voltage will be greater if you use
a coil of wire rather than a straight piece of wire.
SelfInductance
 Now here comes the part that we're really interested in. Suppose
you've got some current running through a coil of wire. According to
the principle of electromagnetism, this current creates a magnetic
field around the coil. What will happen if you change the size of the
current? Well, that will change the strength of the magnetic field.
But according to the principle of electromagnetic induction, when the
magnetic field surrounding a wire changes, a voltage will be induced
across that wire.
 And it turns out that this voltage will always oppose the change
you're making to the current. In other words, if you increase the
current, then a voltage will be induced that will try to decrease the
current. On the other hand, if you decrease the current, then
a voltage will be induced that will try to increase the current.
 The bottom line is: Whenever the current in a coil increases or decreases,
a voltage is induced in the coil, and this induced voltage opposes
the change in current.
 This is called selfinductance; as we've seen, it's the result
of electromagnetism and electromagnetic induction working at the same
time.
Inductance of a Coil
 The size of the voltage induced in a coil depends on a property of
the coil called its selfinductance (or simply inductance).
 The symbol for a coil's inductance is L.
 The unit of inductance is the henry, abbreviated H.

Inductors
 An inductor is a device designed to have a certain amount
of inductance.
 Here's the schematic symbol for an inductor:
 Most of the inductors in our labs look similar to this:
 Typical inductors found in electronic equipment are in the microhenry
(μH) or millihenry (mH) range. Recall that micro means 10^{6} and milli means
10^{3}.
Winding Resistance
 Usually we treat wire as having zero resistance, but in reality wire
does have some resistance. And the longer and thinner a piece of wire
is, the greater its resistance.
 An inductor is simply a coiled piece of very long, very thin wire.
Therefore an inductor will have some resistance, which we call the
inductor's winding resistance.
 The symbol for winding resistance is R_{W}, and
it is measured in ohms.
 You can measure an inductor's winding resistance simply by connecting
an ohmmeter to its two leads, just as you would measure a resistor's
resistance.
 This winding resistance can be fairly largefor example, it's not
unusual to have an inductor whose resistance is 50 Ω or
more. But 50 Ω is still not huge, and we might be able to
ignore it if the inductor is in a circuit whose resistors are much
larger.
 For example, suppose you've got an inductor whose winding
resistance is 50 Ω, and suppose this inductor is
in a series circuit whose total resistance is 2 kΩ.
Then the inductor's winding resistance is only 2.5% of the
circuit's total resistance, small enough that you can probably
ignore it when you're calculating the circuit's current and
voltage drops.
 As a general rule of thumb, if an inductor's winding resistance
is less than about 5% of the resistance that it's in series
with, then you can ignore it.
 An ideal inductor has no winding resistance. In other words, R_{W} = 0 Ω for
an ideal inductor. In most of the following discussion we'll assume
that inductors are ideal, but in a few places we'll mention the effect
of a real inductor's winding resistance.
Inductor Types
 Inductors are classified by the materials used for their cores.
 Common core materials are air, iron, and ferrites.
 Variable inductors are also available. The schematic symbol
has an arrow to show that the component's value can be adjusted:
Chokes and Coils
 Inductors used in highfrequency AC circuits are often called chokes,
or simply coils.
Energy Stored in an Inductor
 Recall that resistors dissipate energy as heat, but
that capacitors store energy.
 Like a capacitor, an inductor stores energy, which can later be
returned to the circuit.
 An ideal inductor (with zero winding resistance)
doesn't dissipate any energy as heat.
 Since R_{W} ≠ 0 Ω for
a real inductor, a real inductor does dissipate
some energy as heat, but generally it's small enough to ignore.
We'll return to this point later when we discuss power in an
inductor.
 A capacitor stores energy in the electric field that
exists between the positive and negative charges stored on its opposite
plates. But an inductor stores energy in the magnetic field that
is created by the current flowing through the inductor.
 The energy W stored by an inductance L is given
by
W = ½ LI^{ 2}
where I is the current through the inductor.
Inductors in Series
Inductors in Parallel
Shortcut Rules for Inductors in Parallel
SeriesParallel Inductors
 As you can probably guess, when you have seriesparallel combinations of
inductors, you find the total equivalent inductance by combining the
rule for inductors in series with the rule for inductors in parallel.
 How about some more pratice problems? (Some of these are a little tricky, so be sure to try them all.) Remember, practice makes perfect!

Series RL Network
 A resistor and inductor connected in series are called a series
RL network.
DC RL Circuit
 An RL circuit is any circuit containing, in addition to a
power supply, just resistors and inductors.
 For now we'll restrict our attention to RL circuits containing DC
voltage sources. We'll refer to such circuits as DC RL circuits.
 Examples: A very simple DC RL circuit just has a resistor,
an inductor, and a voltage source in series:
 Here's a more complicated DC RL circuit:
Behavior of Inductors in DC Circuits
 Just as we have rules of thumb that let us analyze the behavior of
capacitors when they're fully charged or fully discharged, we have
similar rules for inductors.
 Here's an important
rule of thumb that you must memorize:
When an inductor with no current flowing through it is first
switched into a circuit, it behaves like an open circuit.
 So to find currents and voltages in a DC RL circuit whose inductors
have just been switched into the circuit, replace all inductors with
open circuits. Then you'll be left with a circuit containing just a
power supply and resistors, which you can analyze using the skills
you learned in EET 150.
 Here's another important
rule of thumb:
When a constant, unchanging current is flowing through an ideal
inductor, the inductor behaves like a short circuit.
 So to find currents and voltages in a DC RL circuit whose inductors
are carrying a constant, unchanging current, replace all inductors
with short circuits (in other words, with wires). Then you'll be left
with a circuit containing just a power supply and resistors, which
you can analyze using the skills you learned in EET 150.
 Notice that this second rule of thumb applies to ideal inductors
(with zero winding resistance). On the other hand, when a constant,
unchanging current is flowing through a real inductor
(with R_{W} ≠ 0 Ω), the inductor
behaves like a resistor whose resistance is equal to R_{W}.
But as we've seen, this R_{W} is often small enough
that we can ignore it and treat the inductor as a short.
Initial, Transient, SteadyState
 In most practical DC RL circuits, the values of current and voltage
change with time as the current through each inductor changes. Typically
such circuits contain a switch that is initially open, and you're interested
in finding the values of voltage and current after the switch has been
closed.
 To remind ourselves of this fact, we often include an open switch
in schematic drawings of DC RL circuits, as in the following picture:
 Just as with DC RC circuits, we distinguish three time periods in
the behavior of any DC RL circuit:
 the initial period
 the transient period
 the steadystate period
 During the transient period, the circuit's currents and voltages
are changing from their initial values to their final (steadystate)
values.
Initial Currents and Voltages
 The currents and voltages in a circuit at the instant when a switch
is first closed are called the initial currents and initial
voltages.
 In most cases, at this initial instant the circuit's inductors have
no current flowing through them. Therefore, using the first rule of
thumb you learned above, you'll find the
circuit's initial values of voltage and current by replacing the inductors
with opens.
 This is the opposite of capacitors, which initially
behave like short circuits (assuming that they start out being fully
discharged, which is normally the case).
SteadyState Currents & Voltages
 When the switch in a DC RL circuit has been closed for a long time,
currents and voltages have reached their steadystate values.
 According to the second rule of thumb you learned above,
an ideal inductor (with zero winding resistance) behaves like a short
circuit in the steady state. So you find steadystate currents and
voltages in an RL circuit by replacing all ideal inductors with short
circuits.
 Usually we treat inductors as being ideal. But if you want to take
a real inductor's winding resistance into account, then to find steadystate
values you should replace the inductor with a resistor whose resistance
is equal to R_{W}, instead of replacing the inductor
with a short.
 Again, this is the opposite of capacitors, which
behave like open circuits in the steady state.
Transient Currents & Voltages
 When a switch is first closed (or opened) in a DC RL circuit,
currents and voltages change for a short time from their initial values
to their steadystate values. This is very similar to what happens
in a DC RC circuit.
 In the circuit shown below, if we close the switch at time t = 0,
the current will gradually increase from its initial value (zero)
to its steadystate value (which is equal to V_{S}÷R).

More Exponential Curves
 The graphs below show how the current and inductor voltage change
with time in a DC RL circuit after the switch is closed.
 In the plots below, the values on the horizontal and vertical
axes will change depending on the values of resistance, inductance,
and source voltage in a particular circuit, but the shape of
the curves will be the same for all series DC RL circuits.
 The current in a DC RL circuit
starts at 0 and rises to its final value:
 On the other hand, the inductor's voltage starts at its maximum
value and then decreases to 0:
 Notice again that, in each of these graphs, the values change quickly
at first, and then gradually approach a final value.
Time Constant
 For any series RL circuit, the quantity L ÷ R is
called the circuit's time constant. The time constant
is represented by the Greek letter τ,
and it is measured in seconds (s):
τ = L ÷ R
How Long to Reach Steady State?
 The time constant τ is an
indicator of how long i takes to increase from zero to its
steadystate value.
 Here is a useful rule of thumb:
For most practical purposes, we may assume that all quantities
in a DC RL circuit have reached their steadystate values after
five time constants.
 So if a circuit has a time constant of 1 millisecond, then it will
take about 5 milliseconds for the circuit's currents and voltages to
reach their steadystate values.
 Since one time constant is equal to L÷R, we can write
this rule of thumb as an equation:
Time to reach steady state ≈ 5×L÷R
 Notice that in this equation I used a "squiggly equals sign" ≈ to
indicate that this is an approximation. Actually, after five time constants
the current will have risen to about 99.3% of its steadystate value.
For most practical purposes, that's close enough.
DeEnergizing an Inductor
 Up to now we've been talking about energizing an inductor. Similar
comments, but in reverse, apply to the case of discharging a
capacitor. In this case we get what's called an inductive kick, which
has some interesting practical applications , as you'll read about
in this animation:

Unit 2 Review
 This eLesson has covered several important topics, including:
 capacitance
 capacitor specifications
 types of capacitors
 capacitors in series, in paralle, and in seriesparallel
 time constant of a DC RC circuit
 inductance
 types of inductors
 energy stored in an inductor
 inductors in series, in parallel, and in seriesparallel
 time constant of a DC RL circuit.
 To finish the eLesson, take this selftest to check your understanding
of these topics.

Congratulations! You've completed the eLesson for this unit. What's
next?
 Take Quiz #2.
 Perform Lab #2 and turn in a typed
short lab report. (You may wish to review my instructions on
writing short reports.)
 Do Homework #2.
 Keep practicing your skills by playing the games on the Games page.
 Prepare for Unit 3 by reading Chapter 11 of Thomas
Floyd's Principles of Electric Circuits (8th edition).
Then you'll be ready to go on to Unit 3.
Nick Reeder
 Electronics Engineering Technology  Sinclair Community College
Send comments to nick.reeder@sinclair.edu
