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Electrical Components and Circuits

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Chapter 2. Electrical Components and Circuits 2E-2 Recorders Figure 2-27. Schematic of self-balancing recording potentiometer 2E-4 Computers 2E-3 Alphanumeric ... – PowerPoint PPT presentation

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Title: Electrical Components and Circuits


1
Chapter 2.
Electrical Components and Circuits
2
Electric current the motion of a charge
through a medium. Electric units the unit of
charge (or quantity of electricity) C(coulomb)
? 0.001111800g of silver ion ? Charge for
reduction to silver metal. 1Faraday 9.649 x 104
coulombs 1Faraday Deposition of Ag 107.868g of
1 gram equivalent ? (6.02 x 1023 charged
particle), I dQ/dt (Q charge, A ampere)  
Electrical Components
3
  • 2A Direct-Current Circuits and Measurements
  • - Direct current ??? ??? ??
  • Alternating current ??? ????? ???? ?.
  • 2A-1 Laws of Electricity
  • ? ? ??? electrical potential (V) ??? ? ??? ??
    ??? 1?? ??? ????? ? ?.
  • V volt ? joule/conlomb (W/Q V) (IR)
  • R ohm ? R? ?? O(R ?l/A) ? Ohm's
    law
  • G ??? ??(electrical conductance) O-1, S
  • I Ampere
  • P Electrical power. joules/sec, W
  • P dw/dt VdQ/dt VI
  • P (IR)I I2R. joule's law

4
Kirchhoff's Laws - Current low the algebraic
sum of currents around any point in a circuit is
zero. -Voltage low the algebraic sum of the
voltages around a closed electrical loop is
zero.
Power Law P IV P I2R V2/R
5
2A-2 Direct-Current Circuits
  1. Series circuits

Fig 2-1. A battery, a switch, three resistors
in series.
6
? ? D?? kirchhoff's law ?? I4 - I3 0 or I4
I3 , I3 I2 at point C. the current is the
same at all points I I1 I2 I3 I4 ?
Voltage low V - V3 - V2 - V1 0 or V V1
V2 V3 by ohm's law V 1(R1 R2 R3)
IReq ? Req R1 R2 R3   IR1 V1 , V2
IR2 , V3 IR3


V1 I1 R1 IR1
(2-9)
7
Voltage dividers Fig 2-3 a ? series connection
of resistor ? discrete increment
8
- Potentiometer continuously variable
9
2) Parallel Circuits Resistors in parallel at
point A
Kirchhoff's current law to point A I1 I2
I3 - It 0 It I1 I2 I3
10
- Parallel resistances create a current divider.
I1 V/R1 1/R1 G1 Rp
G1 --- ----- ----- --- or I1 It ---
It --- It V/Rp 1/Rp Gp
R1 Gp
11
(Ex. 2-1)
Calculate a) the total resistance, b) the
current from the battery, c) the current present
in each of the resistors, and d) the potential
drop across each of the resistors.
12
  • 1 1 1
  • ( --- --- ) ---
  • R2 R3 R2,3
  • 1 1 1 3
  • --- --- --- --- R2,3 13.3O
  • R 20 40 40

V
15 b) The current V IR I --- -----
0.67A
Rs 22.3 c) V V1 V2 V3 V1 I1R1
6.03 I I2 I3 ??? 9.0
V1 15 x ------------ 6.0V
(9.0 13.3)
13.3 V2 V3 V2,3 15 x ------ 9.0V
22.3 d) R1?? I1 I
0.67A I2 9.0/20 0.45A I3 9.0/40
0.22A
13
2A-3 Direct Current, Voltage, and Resistance
Measurements
Digital Volmeters and Multimeters DArsonval
moving-coil meter ? Digital
Voltmeters and Multimeters. Power Source,
display, A/D converter
14
The Loading Error in Potential Measurements
The Loading Error in Current Measurements
15
See equations 2-19 and 2-20
16
2B Alternating current Circuits
Alternating voltage and current ??? ?? ??? ???
???? ??? ??? ?? ???? ?? ?? ??. ( the simplest
alternating waveform is sine-wave volt or
current.) - Period (Tp) The time required for
the completion of one cycle - Cycle one complete
revolution - Frequency(f) HZ time number of
cycles per second
f 1/tp (2-21)
17
Sinusoidal signals
18
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19
2B-1 Sinusoidal Signals
The AC produced by rotation of a coil in a
magnetic field. A pure sine wave ? ??? ???? ??
??(????) IP? vector? ??. (??? Ip amplitude.)  
?? t ?? 2p radian ? ??? ?? ? ? ? 2p/tp 2pf
Any time t?? instantaneous value ? Vpsin
?t Vp maximum or peak voltage the amplitude
?? ?? ? Ip sin ?t Ip sin 2pft ?? ??
v Vp sin ?t Vp sin 2pft Out of phase by
90o Phase difference phase angle(f) ??? ? Ip
sin(?t f) Ip sin(2pft f)
20
(rms current voltage) DC, AC? ???? ? ??? ??
???? ???? Joule heat DC the effective value of
a sinusoidal, current Report, heating effect of
AC is calculated by averaging I2R losses even
complete cycle
21
1 Hz ?? ?? ??? ??? ?? ohm??
square wave ??? 1.00 ??? 1.00 sine
wave ??? 1.11 ??? 1.41 ??? ???
1.15 ??? 1.73
22
2B-2 Reactance in Electrical Circuits
Reactance - capacitance capacitor
inductance inductor Use ? converting
alternating current to DC or the converse
? discriminating among signals of different
frequencies or separating ac dc
signals. Capacitors ?? a pair of conductors
separated by a thin layer of a dielectric
substance
23
Position 1
Position 2
Figure 2-8. (a) A series RC circuit. Time
response of circuit when switch S is (b) in
position 1 and (c) in position 2.
24
2B-3 Capacitors and Capacitance 1) Capacitance ?
a momentary current ? current ceases ? to be
changed ? switch? 2? discharge.   Capacitor ? ?
? ???? switch off ?? ??? ?? The quantity of
electricity Q ? ? ??, ??, ??, ??? ? ????? ?? ??
25
1 Faraday 1 V? ???? ?? ???? ??? ??? ??? 1 C? ??
capacitance. ( µF, PF)
V 1/C ?idt 1/C? Ip sin wt dt
-1/wc Ip cos wt 1/wc Ip
sin(wt - p/2) ? Vp 1/wc Ip,
V (1/wc) I 1/wc Xc ?
capacitive reactance ?? O
Xc -1/wc, V XcI
26
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27
Rate of current changes in an RC circuit By
Kirchhoff ? voltage law
Vi Vc VR
Vi constant
Vi q/C iR
28
Rate of Voltage Change in an RC circuit
use Ohms law to eq. 2-35
Phase relations between current and voltage in an
RC circuit
29
Rate of Current Potential Change across RL
circuit. RC circuit? ??? ???? ??
VR Vi( I - e-tR/L )
VL Vi e-tR/L
L/R time constant
30
2B-4 Response of Series RC Circuits to Sinusoidal
Inputs Response of series RC RL circuits to
sinusoidal inputs signal (Vs)
31
Ip
32
(1/?C Xc)
At sufficiently high frequencies capacitance, f
become negligible I v are in phase. 1/?C? ??
R? ?? ?? ?. ? ??? ? ?? At very low
frequencies, the phase angle p/2
33
Voltage, current and phase Relationships for
series RL circuit
34
Figure 2-9
35
Capacitive Inductive Reactance impedance
Xc 1/wC 1/2pfC
XL wL
2pfL Impedance Z ?????? ??? ??? ??? ?(????? ???
??) At, RC circuit
Z vR2 Xc2
Z vR2 XL2
Ip Vp/Z
??? ??? ? frequency dependent ? current?
voltage ??? phase difference
36
Figure 2-10
37
ltVector diagrams for Reactive Circuitsgt V? ???
90??. at capacitance V? ??? 90???. at
inductance Z vR2 (XL - Xc)2 Z vR2 Xc2 ,
f -arctan Xc/R Z vR2 XL2 , f -arctan
XL/R Z vR2 (XL Xc)2 f -arctan (XL Xc) /
R (XL gt Xc ? ??) ex) ? peak current ?
voltage drop Z v(50)2 (40 - 20)2 53.8O Ip
10 v/53.8 0.186A Vc 0.186 x 20
3.7V VR 0.186 x 50 9.3V VL 0.186 x
40 7.4V
38
2B-5 Filters Based on RC Circuits High-pass
Low-Pass Filters RC RL circuits ? low f
component? ??? ?? high-f signals? ??? ?? filter?
?? (low pass filter) or ?? ??. ? RC circuit??
high-pass filter Vo across the resistor R
39
(a) high pass filter and (b)low-Pass Filters
40
Low pass filter
41
2B-6 The Response of RC Circuits to Pulsed
Inputs ltResonant Circuitsgt impedance Z? ?? ? XL
Xc ? ? ?? I E/Z E/R ? the condition
of Resonance resonant frequency fo 1/2pfoC
2pfoL ? fo 1/2pvLC ex) (Vp)i 15.0 V (peak
voltage), L 100mH, R 20O, C 1.200µF.
42
Figure 2-13
43
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44
2B-7 Alternating Current, Voltage, and Impedance
Measurements Parallel Resonance Filters
Xc XL fo 1/2pvLC Z of the
parallel circuit Z
vR2 (XLXc/Xc-XL)2 At parallel circuit at
resonance ? Z? ?? ? maximum voltage drop ? ?
tank circuit   Behavior of RC Circuits with
pulsed inputs RC ??? pulse ? ? various form
(with of pulse time const) ??? ??? ?? Simple
Electrical Measurements Galvanometers ? DC? ??,
?? ?? ?? the current in duceol motion of a coil
suspended in a yixed magnetic yiedd. ? D'arsonval
movement or coil. He Ayrton Shunt to vary the
range of a galvanometers p29. ?? ?? ?
measurement of current and voltage.
45
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46
Semiconductor Device
47
  • 2C Semiconductors and Semiconductor Devices
  • Semiconductors
  • Electronic circuits contain one or more nonlinear
    devices such as transistors, semiconductor
    diodes, and vacuum or gas-filled tubes.
  • Nonlinear components rectification (from ac to
    dc ) amplitude modulation or frequency modulation
    vacuum tube ? Semiconductor based diodes and
    transistors ? integrated circuits (Tr, R, C
    conductor)
  • -Semiconductor ?? low cost, low power
    consumption, small heat generation, long life and
    compactness.

48
  • 2C-1 Properties of silicon germanium
    semiconductors.
  • Sufficient thermal agitation occurs at room temp.
    to liberate an occasional electron from its
    bonded state, leaving it free to more through the
    crystal lattice and thus to conduct electricity.
  • Hole positively charged region.
  • -Electron negatively charged region.
  • -Hole electron ? ???? ??.
  • -Doping of arsenic or antimony (Group ?) ? n type
  • of indium or gallium (Group ?) ? p
    type
  • Positive holes are less mobile them free
    electrons.
  • Conductivity of n type gtconductivity of p type.
  •  

49
2C-2 . Semiconductor Diodes Pn junction motion ?
diode is a nonlinear device that has greater
conductance in one direction than in another.

Figure 2-15 A pn junction diode (c) forward -
bias (d) reverse - bias ? depletion layer ??
conductance 10-610-8
50
Figure 2-16 I - V cures for semiconductor Diodes
The voltage at which the sharp increase in
current occurs under reverse bias is called the
Zener breakdown voltage.
51
2C-3 Transistors Amplifying device -Bipolar
-Field effect transistor. ? Bipolar Tr. pnp,
npn tr.
52
Figure 2-17.
The mechanism of amplification with a bipolar
transistor. pnp on ? n layer 0.02mm thickness,
pgtgtn layer. (??? ??), ?The concentration of
holes in p gtgt that of electrons in n layer
53
Figure 2-18.
54
? P-type emitter junction ?? hole ?? ? ??? hole ?
very thin n-type base ? ?? - electron ? ?? (base
current IB??) ? ???? hole ? base? ?? drift ??
collector junction ?? attracting ? ??? power
supply??? ?? electron ? combined ?? ?? ??
(Ic) The no of current carrying holes is a fixed
multiple of the number of electrons supplied by
the input base current.
55
Field Effect Transistors (FET) FET - The
insulated gate field effect transistor.
?1091014 ? ? imput impedence ? MOSFET (metal
oxide semiconductor FET) n- chanel MOSFET The
gate is a cylindrical p-type semiconductor
surrounding a center core of n -doped material
called the channel. Two isolated n regions are
formed in a p-type substrate. ?? n.p regions ?
silicon dioxide? insulating
56
Figure 2-19.
57
(n-channel junction FET) current enhancement in
brought about by application of a positive
potential to the gate Gate ? " induce -
substrate channel below the layer of
SiO2 Depletion mode ?in the absence of a gate
voltage reverse bias is applied to the gate the
supply of electrons in the channel is depleted. ?
channel ?? ???????. The width of the reverse
biased gate junction determined (the wide of the
channel and consequently). The magnitude of the
current between source and drain.
58
2D Power Supplies and Regulators most ps contains
a voltage regulator.
Figure 2-20.
59
2D-1 Transformers VX 115 X N2/N1 N2 and N1 are
the no of turns in the secondary and primary
coils.
2D-2 Rectifiers ?Half wave rectifier ?Full wave
rectifier ?bridge rectifier ???? ? ??
60
Figure 2-21.
61
D2, D3 ? conduct on the alternate D4 and D1
conduct Since two diodes are in series with the
load, the output voltage is reduced by twice the
diode drop.
Figure 2-22.
62
2D-2 Rectifiers and Filters
Figure 2-23.
In order to minimize the current fluctuations. L
section filter S ? ?? C? ?? ??. ? peak to peak
ripple can be reduced.
63
2D-3 Voltage Regulators
Figure 2-24.
Zener diode breakdown condition ??? ??. Under
breakdown condition, a current change of 20 to 30
mA may result from a potential change of 0.1 V or
less.
64
2E Readout Devices
Figure 2-25. Basic analog oscilloscope component
65
2E-1 Oscilloscopes Cathode-Ray Tubes
Horizontal and vertical Control Plates.
Trigger Control.
Figure 2-26. Schematic of a CRT
66
2E-2 Recorders
Figure 2-27. Schematic of self-balancing
recording potentiometer
67
2E-3 Alphanumeric Displays
2E-4 Computers
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