balanced. The major disadvantage of quarter-wave sections is that they
work only at specific frequencies. But this is often offset by the ease
with which they are constructed, if radio equipment is to be used at only
one frequency, or at odd-harmonic freq
lags Y by 45 degrees. B. X leads Y by 45 degrees. C. X lags Y by 135
degrees. D. X leads Y by 135 degrees. 228 Phase 12-12 Illustration for
quiz question 15. 16. Which of the drawings in Fig. 12-13 represents the
situation of Fig. 12-12? A. A. B. B. C. C.
as nonlinearity. Whenever there is nonlinearity of any kind in a circuit
that is, whenever the output waveform is shaped differently from the
input waveformthere will be harmonic frequencies in the output.
These are waves at integer multiples of the input
and at other times like an insulator in the same circuit. The term
semiconductor arises from the ability of these materials to conduct part
time. Their versatility lies in the fact that the conductivity can be
controlled to produce effects such as amplifi
jBC j0.00500 j0.00500 j0 There is no susceptance. Because the
conductance is also zero (there is nothing else in parallel with the coil
and capacitor that might conduct), the admittance vector is 0 j0. This
situation, in which there is no conductance and
or 1:2.45. This is the primary-tosecondary turns ratio for the transformer.
The secondary winding has 2.45 times as many turns as the primary
winding. Problem 18-4 A transformer has a primary-to-secondary turns
ratio of 4.00:1. The load, connected to the
Antennas Many types of antennas exhibit resonant properties. The
simplest type of resonant antenna, and the only kind that will be
mentioned here, is the center-fed, half-wavelength dipole antenna (Fig.
17-14). The length Lft, in feet, for a 1/2-wave dipo
until the forward bias voltage is at least as great as the forward
breakover voltage. The flip side is that the diode will always conduct
when the forward bias exceeds the breakover value. In this case, the
voltage across the diode will be constant: 0.3 V
about the peak inverse voltage (PIV) or peak reverse voltage (PRV)
specification. Its important that rectifier diodes have PIV great enough
so that avalanche effect will not occur (or even come close to happening)
during any part of the ac cycle. Otherwis
C. Reactance. D. Admittance. 16. Absolute-value impedance is equal to
the square root of: A. G2 B2 B. R2 X2. C. Zo. D. Y. 17. Inductive
susceptance is measured in: A. Ohms. B. Henrys. C. Farads. D. Siemens.
18. Capacitive susceptance is: A. Positive and r
Perhaps you have seen the modulation envelope of such a signal
displayed on an oscilloscope. Imaginary power If an ac circuit contains
reactance, things get interesting. The rate of energy expenditure is the
same as the VA power in a pure resistance. But
peak, in phase opposition with respect to the composites. D. 2 V peak, in
phase opposition with respect to the composites. 10. Shifting the phase
of an ac sine wave by 90 degrees is the same thing as: A. Moving it to
the right or left by a full cycle. B.
defined, constant avalanche voltages. Suppose a certain Zener diode has
an avalanche voltage, also called the Zener voltage, of 50 V. If a reverse
bias is applied to the P-N junction, the diode acts as an open circuit
below 50 V. When the voltage reaches
is less than the secondary impedance. C. The secondary voltage is
greater than the primary voltage. D. The output frequency is higher than
the input frequency. E. The output frequency is lower than the input
frequency. 33. A capacitor of 470 pF is in para
equal to X/R. Therefore, the phase angle is arctan (X/R) arctan (30/50)
arctan (0.60) 31 degrees. The power factor is the cosine of this angle;
PF cos (31) 0.86 86 percent. Problem 17-7 A circuit has a resistance
of 30 and an inductive reactance of 40 . W
jX 80 j40. Putting it all together When youre confronted with a
parallel RLC circuit, and you want to know the complex impedance R
jX, take these steps: 1. Find the conductance G = 1/R for the resistor. (It
will be positive or zero.) 2. Find the susceptan
908 j908 The susceptance, BL is equal to 1/XL Therefore, BL 1/j908
j0. 00110. Remember that inductive susceptance is negative. The
formula for inductive susceptance is similar to that for capacitive
reactance: BL 1/(6.28fl) siemens j(1/(6.28fL) Admittance
form by various methods, and the value tailored as desired. Metal-film
units can be made to have nearly exact values. Film type resistors
usually have low to medium-high resistance. A major advantage of film
type resistors is that they, like carbon-compos
about: A. 8. B. 10. C. 16. D. 18. Quiz 19 4. An ion: A. Is electrically
neutral. B. Has positive electric charge. C. Has negative electric charge.
D. Might have either a positive or negative charge. 5. An isotope: A. Is
electrically neutral. B. Has positi
will be 84 mm to the right of the origin, or intersection of the original
two perpendicular lines. The XL mark will be 68 mm up from the origin.
Draw a line connecting the two hash marks, as shown in Fig. 13-12. This
line will run at a slant, and will for
j3) mean there is net capacitance. 276 Impedance and admittance
Admittance is the complex composite of conductance and susceptance.
Thus, admittance takes the form Y G jB The j factor might be negative,
of course, so there are times youll write Y G jB. Pa
Tpri/Tsec If the input and output, or source and load, impedances are
purely resistive, and are denoted by Zpri (at the primary winding) and
Zsec (at the secondary), then Zpri/Zsec (Tpri/Tsec)2 and Zpri/Zsec
(Epri/Esec)2 The inverses of these formulas, in
waveforms are sometimes seen at certain points in electronic circuitry.
The ac generator Alternating current is easily generated by means of a
rotating magnet in a coil of wire (Fig. 9-14A), or by a rotating coil of
wire inside a powerful magnet (Fig. 9-1
50.0 70.5 V. The voltage drop across the reactance is the product of the
current and the reactance: EX IX 1.41 ( 50.0) 70.5. This is an ac
voltage of equal magnitude to that across the resistance. But the phase is
different. The voltages across the resist
generated. Not surprisingly, high-energy power plants have bigger
transformers that develop higher voltages than low-energy, local power
plants. These transformers must be able to handle not only huge
voltages, but large currents as well. Their primaries
10 In a matched line, E/I is constant, although both E and I decrease
with increasing distance from the source. Standing waves If the load is
not matched to the line, the current and voltage vary in a complicated
way along the length of the line. In some
the capacitive part). This is illustrated in Fig. 16-2. When vectors dont
lie along a single line, you need to use vector addition to be sure that you
get the correct resultant. Fortunately, this isnt hard. In Fig. 16-3, the
geometry of vector addition is
piece of transmission line is called a quarter-wave section. When a
quarter-wave section is short-circuited at the far end, it acts like a
parallel-resonant LC circuit, and has a high impedance at the resonant
frequency fo. When it is open at the far end,
D. Causes the material to stop conducting. 12. If a material has low
resistance: A. It is a good conductor. B. It is a poor conductor. C. The
current flows mainly in the form of holes. D. Current can flow only in
one direction. 13. A coulomb: A. Represent
this is visually apparent. A right triangle is formed by the resistance
vector R (the base), the reactance vector jX (the height) and the
absolute-value impedance Z (the hypotenuse). The cosine of the phase
angle is equal to the ratio of the base length t
work with them. E. Cancel out. 10. A wave has a frequency of 200 kHz.
How many degrees of phase change occur in a microsecond (a millionth
of a second)? A. 180 degrees. B. 144 degrees. C. 120 degrees. D. 90
degrees. E. 72 degrees. 11. At a frequency of 2.
type. Semiconductor materials 361 Doping For a semiconductor material
to have the properties needed to work in electronic components,
impurities are usually added. The impurities cause the material to
conduct currents in certain ways. The addition of an i
that is analogous to the situation with the RL plane from the previous
chapter. The resistance ray and the capacitive-reactance ray can be
placed end to end at right angles to make a quarter plane called the RC
plane (Fig. 14-5). Resistance is plotted hor
j0.00282. B. 0 j0.00194. C. 0 j0.00194. D. 0 j0.00758. 12. A vector
pointing southeast in the GB plane would indicate the following: A.
Pure conductance, zero susceptance. B. Conductance and inductive
susceptance. C. Conductance and capacitive susceptance
10.0) This can be solved easily enough. Divide out C 1/6280 on your
calculator, and youll get C 0.000159. Because the frequency is given in
megahertz, this capacitance comes out in microfarads, so that C
0.000159 F. You might rather say that this is 159 p