CM 4358 Module 1-5 (Midterm)
Because voltage is proportional to the sine of the angle, as the loop goes 360° around the circle the voltage will increase from 0 to its maximum at ___°, back to 0 at ___°, down to its maximum negative value at 270°, and back up to 0 at ___°.
90 180 360
In a capacitive circuit, the current leads the voltage by
90 degrees
In an inductive circuit, the voltage leads the current by ________ ________, which means that the voltage begins at its maximum ________ value
90 degrees : positive
If a vector diagram shows a right angle, the voltages are
90 degrees out of phase
is a coil of wire that may be wound on a core of metal or paper, or it may be self-supporting
An inductor
The circuit values can be found using Ohm's law, where
I (current) = E(voltage)/R (resistance)
is calculated from all the values in a sine wave for one alternation or half cycle
The average value
Core material -
The core of the coil can be either a magnetic material (such as iron) or a nonmagnetic material (such as paper or air). Coils wound on a magnetic core produce a stronger magnetic field than those with non-magnetic cores, giving them higher values of inductance.
the material between the capacitor plates in which the electric field appears.
The dielectric
Winding the coil in layers -
The more layers used to form a coil, the greater the effect the magnetic field has on the conductor. Layering a coil can increase the inductance
The opposing force that an inductor presents to the flow of alternating current
The name given to this force is inductive reactance because it is the reaction of the inductor to alternating current.
the time (t) required to complete one cycle
The period of a waveform
expresses the ratio of the electric field strength in a dielectric to that in a vacuum.
Relative permittivity
In capacitive circuits, the ________ leads the voltage by 90°
current
One hertz equals one
cycle per second (cps)
the value of the AC current or voltage wave that indicates the same energy transfer as an equivalent direct current (DC) or voltage
effective value
Capacitance is measured in smaller values are measured in
farads (F) microfarads (μF)
The number of cycles per second is the
frequency
The period is the inverse of
frequency
cycles / seconds =
frequency (cycles per second (Hz))
the number of times per second an identical pattern repeats itself.
frequency of a waveform
Voltage is produced when a conductor cuts through the lines of
fux
The direct comparison between DC and AC is in the
heating effect of the two currents.
The unit for inductance is the
henry (H)
The unit of frequency is
hertz (Hz)
Capacitors are used in series to provide a
higher voltage breakdown rating for the combination
If a vector diagram is flat, the voltages are
in phase
Connecting capacitors in series is equivalent to
increasing the thickness of the dielectric.
when the flux moves at a higher speed it can
induce more voltage
The faster the current changes, the higher the
induced voltage becomes
Reactive power is that portion of the apparent power that is caused by
inductors and capacitors in the circuit.
If resistance is changed, it will affect only the
magnitude of the current
When voltages are in phase, they reach their
maximum and minimum values at the same time
cuts across the conductor that is providing the current, producing induced voltage in the wire itself
moving flux
Inductors and capacitors consume
no power
Any waveform that is not a sine or cosine is known as a
nonsinusoidal waveform.
Lines of flux run from ________ to ________ in a generator.
north : south
Inductive reactance is measured in
ohms
Two alternations form
one cycle
One henry is the amount of inductance that allows
one volt to be induced when the current changes at the rate of one ampere per second
The capacitance of the capacitor is increased when the
permittivity of the dielectric is increased.
The inductance of a coil or inductor depends on its
physical construction
The voltage across each capacitor in series is inversely
proportional to its capacitance.
The opposing force that an inductor presents to the flow of alternating current cannot be called ________ because it is not the result of friction within a conductor.
resistance
The voltage is the ________ across the parallel capacitors.
same
The conductor loop rotates through the magnetic field to generate the induced AC voltage across its open terminals. The magnetic flux shown is vertical.
simple one loop rotary generator
The magnitude of the voltage produced will be proportional to the
sine of the angle
However, in many electronic applications, other wave shapes are important. Common examples are the
square wave and sawtooth wave.
The voltage and current in a capacitive AC circuit follow a
standard sine wave.
The only function of inductors and capacitors is to
store and release energy.
If the generator is operated at a constant rpm, the voltage produced at any moment will depend on
the angle at which the conductor is cutting the field at that instant.
In an AC circuit with only resistance, the current variations are in phase with
the applied voltage.
what is measured between two points having the same amplitude and varying in the same direction.
the cycle
No work is performed by reactive power; the power is stored in
the inductors and capacitors, then returned to the circuit.
Apparent power is the product of
the source voltage and current
A capacitor consists of
two conductors separated by an insulating material
Apparent power is measured in
volt-amperes (VA).
In inductive circuits, the ________ leads the current by 90°
voltage
The capacitor begins to charge when and stops when
voltage is applied to the circuit the potential difference across the capacitor is equal to the applied voltage
Reactive power is measured in
voltamperes-reactive (VARs).
True power measures the power consumed by resistance and is measured in
watts (W)
When the conductor is moving parallel to the lines of flux (angle of 0°), it is not cutting any of them, and the voltage will be
zero
When voltages are 90 degrees out of phase, one is at
zero while the other is at its maximum value.
Length of the core -
When the length of the core is decreased, the turn spacing is decreased, increasing the inductance of the coil.
Area of the plates in a capacitor
- Larger plates will produce a greater capacitance than smaller ones.
Two principles form the basis of all electromagnetic phenomena:
1. An electric current in a conductor creates a magnetic field surrounding that conductor. 2. Relative motion between the conductor and a magnetic field creates a voltage in the conductor.
The capacitance of a capacitor is determined by three factors:
1. Area of the plates 2. Distance between plates 3. Dielectric permittivity
Some of the factors affecting inductance are: 4
1. Number of turns 2. The spacing of the turns on a coil 3. Coil diameter 4. Length of the core 5. Core material 6. Winding the coil in layers
The rate at which the conductor cuts the magnetic field depends on: (2)
1. the speed of the generator in revolutions per minute (rpm) 2. The angle at which the conductor is traveling through the field.
There are three factors affecting the magnitude of voltage developed by a conductor through a magnetic field:
1. the strength of the magnetic field 2. the length of the conductor 3. The rate at which the conductor cuts directly across or perpendicular to the magnetic field.
is a device that stores an electric charge in a dielectric material.
A capacitor
The spacing of the turns on a coil.
A coil that has widely-spaced turns has a lower inductance than one that has the same number of more closely-spaced turns. The reason for this higher inductance is that the closely-wound turns produce a more concentrated magnetic field, causing the coil to exhibit a greater inductance.
a maximum value of voltage or current.
A peak value
One complete waveform or cycle includes a complete set of variations, with two alternations in polarity.
AC Waveforms
the current is continuously changing; periodically high, periodically low, and periodically zero
AC circuit
The sine wave is the basic waveform for ________ ________. This waveform is produced by a rotary generator (circular motion), as the output is proportional to the ________ ________ ________
AC variations: angle of rotation
its associated voltage reverses between positive and negative polarities and varies in amplitude with time.
Alternating current (AC)
_______ is the ability to store a charge.
Capacitance
Capacitors in Series equation
Ct = (1 / ((1/C1) + (1/C2)))
heat produced is steady in a
DC circuit
the result of the expanding and collapsing field caused by the changing current.
Inductance
what is the circuit characteristic that opposes the change of current flow.
Inductance
Light emitting diode
LED stands for
What can be compared for voltages with the same frequency
Phase relationships
Number of turns -
The greater the number of turns, the greater the inductance
Coil diameter -
The inductance increases directly as the crosssectional area of the coil increases.
distance traveled by a waveform during one period.
The wavelength
the current maintains a steady amplitude
a DC circuit
When connecting capacitors in parallel, the total capacitance is calculated by
adding the individual values CT = C1 + C2
Each time the waveform changes from zero to a peak value and back to zero is called an
alternation
AC wave the current changes direction during each ________
alternation.
The current value depends on the
applied voltage and the resistance.
heat is produced by ________ alternations of the AC wave
both
In a capacitive circuit driven by an AC voltage source, the voltage and charge on the capacitor are
both continuously changing.
DC is blocked by a
capacitor
Current will flow in a capacitive circuit with AC voltage applied because of the capacitor charge and discharge current. With alternating voltage applied, the capacitor alternately charges and discharges. The cycles of charge and discharge current provide alternating current in the circuit at the same frequency as the applied voltage. The amount of capacitance in the circuit will determine how much current is allowed to flow
capacitor and discharge
In storing a charge, a capacitor opposes a ________ ________ ________
change in voltage
two conductors separated by an insulating material called a
dielectric.
Notice that at 180°the polarity reverses. This is because the conductor has turned completely around and is now cutting the lines of flux in the ________ ________
opposite direction
It is at zero when ________ to the lines of flux and at its maximum when ________ to the lines of flux.
parallel : perpendicular
