基礎(chǔ)電子學(xué)文檔閱讀

基

礎(chǔ)

電

子

學(xué)氣動(dòng)工程師用Potential

Difference

is

the

difference

in

voltage

between

two

points

in

acircuit.

This

is

still

the

case

whenone

or

both

of

the

values

are

negative.

For

examplethe

potential

difference

between

apoint

in

acircuit

at

10Vand

another

point

in

the

same

circuit

at

0V

is

of

course

10V.

The

potential

difference

is

also

10Vbetween

points

at

100V

and

90V,

0V

and

-10V,

and

-10V

and

-20V.電壓電路中的電壓就象氣路中的壓力電壓越高，作用力就越大符號(hào)為V單位：伏特V

毫伏(mV)1000

(mV)

=

1

V微伏(礦)

1,000,000(礦)=1

V電路中，兩點(diǎn)之間的電勢(shì)差就是電壓電路中下列兩點(diǎn)之間的電勢(shì)差都是+10V:10V和0V100V和90V0V和-10V-10V和-20V電壓并聯(lián)電路兩端的電勢(shì)差保持不變OFF11000000VV

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V0

VCurrent

in

an

electrical

circuit

can

be

likened

to

flow

of

free

air

in

apneumatic

circuit.

The

higher

the

current

the

greater

is

the

quantity

of

electricity

flowing.The

symbol

used

is

I

and

is

measured

in

Amperes

or

Amps

(

A

)

this

can

be

subdivided1000

milliamps

(

mA

)=

1A1,000,000

microamps(礎(chǔ))=1

AEngineers

work

withconventional

current

flow

which

is

frompositive

to

negative

and

is

the

direction

indicated

by

the

arrows

on

most

symbols

in

circuitdiagrams.The

actual

flow

of

electrons

is

in

the

opposite

direction

and

anunderstanding

of

this

is

necessary

when

lookingat

how

individual

electronic

components

work電流電路中的電流就象氣路中的氣流電流越大，通過(guò)的電量就越多符號(hào)為

I單位：安培(A)毫安(mA)

1000

mA=1

A微安(礎(chǔ))

1,000,000礎(chǔ)=1

A電流的方向是從正極至負(fù)極電路圖中，大多數(shù)符號(hào)上用箭頭表示電流的方向電子的實(shí)際移動(dòng)方向與電流方向相反電流串聯(lián)電路中，電流處處相等測(cè)量電流，電流表必須串聯(lián)在電路中+

V0

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V0

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IDM91Resistance

in

an

electrical

circuit

can

be

likened

to

restriction

in

a

pneumatic

circuit,

it

hasa

limiting

effect.The

symbol

R

is

used

for

resistance

and

it

is

measured

in

OhmsLarger

Units

are1k

(kilo

ohm)

=

1000

Ohms1M

(mega

ohm)

=

1,000,000

Ohms電阻電路中的電阻就象氣路中的節(jié)流，有限制的作用符號(hào)為R單位：歐姆(ohm)千歐(k

ohm)1k

ohm

=

1000

Ohms兆歐(M

ohms)1M

ohm=1,000,000Ohms電路圖和其它文件中，電阻值可以用不同的形式表示，下列電阻器均為4700

歐姆R4.7KR4K74R7The

circuit

symbol

for

a

resistor

is

shownin

the

illustration.

The

valueof

the

resistanceis

shownagainst

the

symbol電阻器實(shí)際的電阻器上常用不同的色碼來(lái)表示它的電阻值，右面電阻器均為4700歐姆底色沒(méi)有規(guī)定，但可分辨出不同的制造商Byconnecting

resistors

in

series

a

largerresistance

is

obtained串聯(lián)電阻器電阻器按串聯(lián)方法連接，將得到較大的電阻總電阻R=R1+R2+R3R=200+200+200R=600歐姆R1R2R3R

200R

200R

200并聯(lián)電阻器電阻器按并聯(lián)方法連接，將得到較小的電阻總電阻RR=100歐姆1

=

1

+

1

+

1R 300

300

300R1R

300R2R

300R3R

300+/-

1%+/-

2%電阻器的色碼顏色乘數(shù)容差

溫度0.01+/-10%0.1+/-

5%78901110210031000410000510000061000000100ppm

50ppm第5或6條色碼第3或4條色碼第1和2條色碼或第1,2和3條色碼第4或5條色碼Ohms

law

provides

the

mathematical

relationship

between

potential

difference,

current

flow

and

the

resistance

in

an

electrical

circuit,

where

R

is

in

ohms,

V

isin

volts

and

I

is

in

ampsR=V/IFromthis

we

can

see

that

fora

circuit

witha

constant

resistance

the

current

flow

will

be

directly

proportional

to

the

potential

differenceIf

the

potential

difference

is

held

constant

the

current

will

varyinverselywith

the

resistanceIf

the

current

is

held

constant

the

voltage

must

vary

in

direct

proportion

to

the

resistance.歐姆定律歐姆定律告訴我們，一個(gè)電路中，電壓、電流和電阻之間的數(shù)學(xué)關(guān)系上面公式中采用的單位：R=歐姆

V=伏特

I=安培VR=

I如果電阻不變，電流與電壓成正比，即R=V/I如果電壓保持不變，電流與電阻成反比，即V=IR如果電流不變，電壓與電阻成正比，即I=V/RAn

important

basic

circuit

is

the

potential

divider.

This

circuit

uses

two

resistors

wired

in

series

witha

tapping

between

them.

The

purpose

of

a

potential

divideris

to

drop

the

circuit

supply

voltage

to

a

lower

output

voltage

for

feeding

some

other

device,

for

example

the

base

of

a

transistor.

Whenmaking

a

calculationassume

that

there

is

no

load

connected

to

the

output.

In

practiceaload

will

be

drawingsome

current

so

the

designed

current

through

R1

+

R2

should

be

kepthighby

comparison

so

that

V

Out

is

relatively

unaffected

by

an

on

or

off

condition

of

the

load.

As

a

guide

about

10

:

1.Note

that

the

proportion

of

R1

:

R2

determine

V

Out

and

the

value

of

R1

and

R2

determine

how

much

current

will

flow.分壓器這個(gè)電路中，采用兩個(gè)串聯(lián)電阻，中間有一個(gè)抽頭用來(lái)降低電壓，然后提供給電路的其它部分，譬如三極管的基極假如輸出端沒(méi)有連接電阻R1+R2決定電流R1與R2的電阻值之比，決定輸出電壓+V輸入0

V+V輸出R1R2For

the

potential

divider

shown,

the

voltage

V1

is

9

volts

and

the

load

when

connected

will

draw

about

1

mA

at2

V.

We

will

design

for

the

resistors

to

passten

timesas

much

current

(10

mA).

To

obtain

a

voltage

V

Out

of

2

volts

the

values

of

resistors

R1

and

R2

can

be

calculated

asfollows

using

ohms

law.V

=

I

R

V

in

=

I

[

R1

+

R2

],

9

=

0.01

[

R1

+

R2

],

[

R1

+

R2

]

=

900V

Out

=

I

R2,

2

=

0.01

R2,

R2

=

200R1

=900

-

200,

R1

=

700分壓器(計(jì)算)輸入電壓V等于9伏特當(dāng)連接負(fù)載時(shí)，2

V時(shí)約需1

mA電阻器設(shè)計(jì)時(shí)，應(yīng)考慮用十倍的電流(10

mA)算出R1+R2V=I

R

V

入=I[R1+R2]9

=

0.01

[

R1

+

R2

]R1+R2=900

歐姆算出R2V

出=I

R2,2=0.01R2

R2=200

歐姆算出R1R1=900-200,

R1=700

歐姆+9

V

入0

V+2

V

出R1R2Load萬(wàn)用表測(cè)量：電壓

電阻

低電流高電流電流通過(guò)的連續(xù)路徑OFF1000V200V20V2V750V200V20AuADC200mV200uA

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200mA200mAAC

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POWER

OFFISO

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IDM91The

effects

of

electro

magnetismare

made

use

of

in

many

devices

and

components

such

as

transformers,

inductors,

relays,

and

solenoids

etc.Whenever

current

is

flowing

in

aconductor

amagnetic

field

is

set

up

around

it.

Current

flowing

away

from

the

observation

point

(

the

flight

end

of

the

arrow

)produces

a

clockwise

field

and

current

flowing

towards

the

observation

point

(

the

point

end

of

the

arrow

)

produces

an

anti-clockwise

field.電磁當(dāng)導(dǎo)體上流經(jīng)電流時(shí)，它的周圍會(huì)產(chǎn)生磁場(chǎng)當(dāng)電流流入時(shí)(用箭尾X表示)，產(chǎn)生順時(shí)針?lè)较虻拇艌?chǎng)當(dāng)電流流出時(shí)(用箭頭?表示)，產(chǎn)生逆時(shí)針?lè)较虻拇艌?chǎng)磁效應(yīng)用于很多元件上，如變壓器、感應(yīng)器、繼電器和電磁鐵等When

amagnetic

field

is

present

in

air

it

is

wide

ranging

and

thinned

out.

Itis

strong

close

to

the

source

and

becomes

progressively

weaker

the

further

it

rangesout.

Wherever

there

is

a

ferrous

metal

path

the

field

will

be

concentrated

in

it

and

there

will

be

very

much

less

stray

magnetic

field.

Softiron

is

used

in

many

electro-magnetic

devices

to

conduct

the

magnetic

field.

Thereason

for

this

isthat

when

the

source

of

the

field

is

removed

the

iron

will

notretain

any

residual

magnetism.

This

is

in

contrast

to

carbon

steel

which

will

become

progressively

more

of

a

permanent

magnet

each

time

itis

subjected

to

a

magnetic

field.

The

illustration

shows

the

principle

of

a

simple

electro-magnet.電磁鐵有色金屬能夠聚集磁場(chǎng)很多電磁裝置上常使用軟鐵，因?yàn)榫€圈上的電流撤銷后，軟鐵不會(huì)保持磁性右圖表示一個(gè)簡(jiǎn)單電磁鐵的原理SNWhenwire

is

coiled

roundasoft

iron

core

and

connected

to

a

power

source

the

core

becomes

magnetic.

When

the

power

source

is

disconnected

themagnetic

field

is

lost.

This

principle

is

used

in

many

devices

including

relays

and

solenoids.電磁鐵有色金屬能夠聚集磁場(chǎng)很多電磁裝置上常使用軟鐵，因?yàn)檐涜F會(huì)傳導(dǎo)磁場(chǎng)右圖表示一個(gè)簡(jiǎn)單電磁鐵的原理SNThe

magnetic

field

produced

by

current

flowing

in

each

turn

of

the

coils

combine

together

to

polarise

the

core.

The

more

turns

the

more

powerful

the

electro-magnet

will

be

including

coils

wound

on

top

of

each

other.電磁鐵從線圈的剖面圖中，我們看到電流流過(guò)線圈的每一部分都會(huì)產(chǎn)生磁場(chǎng)，聚集后形成軟鐵上的磁極SNThe

unit

of

measurement

for

inductance

is

the

Henry

HThis

can

be

sub-divided1,000

millihenries

(mH)

=

1H1,000,000

microhenries(礖)=1HFor

an

induced

e.m.f.

of

1V

anda

rate

of

current

changeof

1A

the

Inductance

is

1HInductance

is

the

effect

of

producing

or

inducing

an

e.m.f.

in

a

circuit

when

an

increasing

or

decreasing

magnetic

flux

is

passingthrough

the

circuit.電感電感的單位是亨利

H單位的互換：1,000毫亨(mH)=1H1,000,000微亨(礖)=

1H符號(hào)為

L下圖是它在電路中的畫(huà)法電路中的電流變化時(shí)(上升或下降)，它的磁場(chǎng)就變化的這種效應(yīng)，稱為電感An

inductor

is

any

coil

of

wire

usuallywith

a

soft

iron

core

orformer.

Consider

connecting

an

inductor

in

ad.c.

circuit

as

shown.Whenthe

switch

is

closed

the

full

source

voltage

is

applied

across

the

coil

and

as

the

current

starts

to

flow

an

electro-magnetic

field

starts

to

build

up.

Theincreasing

flux

of

this

field

is

moving

through

the

coil

of

wire

that

is

producing

it

and

will

induce

an

e.m.f.

in

the

coil.

This

however

isof

opposite

polarity

to

thevoltage

that

is

generating

the

field.

The

induced

e.m.f.

will

initially

almost

completely

oppose

the

source

voltage

to

the

point

where

the

net

forward

voltagethroughthe

lowresistance

of

the

coil

is

at

the

minimumto

sustain

current

growth.

This

rate

is

self

regulating

dependant

on

the

efficiency

of

the

inductor,because

if

the

current

were

to

grow

too

fast,

the

induced

voltage

increases

to

slow

it

down

and

if

it

were

to

grow

more

slowlythe

induced

voltage

decreasesto

speed

it

up.

Whenthe

maximumcurrent

for

the

coil

is

reached

there

will

be

no

change

in

flux

and

the

induced

e.m.f.

will

be

zero.電感(直流d.c.電路)在這個(gè)線路中，不會(huì)立即達(dá)到全功率當(dāng)開(kāi)關(guān)閉合的瞬間，電感器上的磁場(chǎng)逐步增強(qiáng)由于反向的電感電流，使這種增強(qiáng)逐漸減慢當(dāng)磁場(chǎng)停止增強(qiáng)時(shí)，只有很小電阻的線圈，沒(méi)有電感電流時(shí)間LThis

mechanical

analogy

to

inductance

may

help

understand

it.Imagine

a

constant

force

pushing

a

heavy

trolley

fromrestatpoint

A

to

full

speed

atpoint

B

and

beyond.At

first

the

speed

will

be

low

due

to

the

inertia

of

the

massof

the

trolley.

As

speed

builds

up

so

more

of

the

force

is

used

to

maintain

speed

against

losses

suchas

rollingresistance

and

less

is

available

for

acceleration.

At

point

B

all

of

the

force

is

required

to

maintain

the

trolley

at

maximumspeed

and

there

is

no

furtheracceleration.

In

this

analogy

of

an

inductor

at

switch

on,

in

ad.c.

circuit,

speed

is

current,

force

is

voltage,

inertia

is

inductive

reactance

and

the

rollingresistance

etc.

is

resistance

of

the

coil.電感(機(jī)械比喻)恒力F推一輛沉重的小車由靜止A點(diǎn)至B點(diǎn)，B點(diǎn)時(shí)達(dá)到全速力就象電壓，所有時(shí)間均有速度就象電流，它是逐漸增加，直至最大慣性就象感抗?jié)L動(dòng)阻力等就象線圈的電阻MABF速度時(shí)間ABIn

an

a.c.

circuit

the

current

also

has

adelaybehind

the

source

voltage

and

since

the

voltage

is

changing

so

the

current

is

changing

but

delayed

behind

it.

In

atheoretical

a.c.

circuit

where

there

is

only

inductance

L

(

resistance

is

ignored)

the

current

will

be

90o

aquarterof

acycle

behind

the

voltage.

The

inducedvoltage

will

almost

be

in

complete

opposition

to

the

source

voltage.電感(交流a.c.電路)電流滯后電壓可看到有-90O

相位差交流頻率增加，電流波幅減小(使電流增加時(shí)間減少)電感電磁場(chǎng)電壓電流-90o相位差A(yù)gain

the

mechanicalanalogy

may

help.Imagine

that

an

alternating

force

is

goingto

be

applied

to

the

trolley

so

that

it

will

reciprocate

between

points

A

and

C.

For

each

cycle

the

force

is

atamaximumas

the

trolley

starts

to

move

to

the

right

but

reduces

to

zero

as

the

trolley

reaches

maximumvelocity

at

point

B

the

force

then

goes

negative

to

startretarding

the

trolley

and

a

maximumnegative

force

is

reached

at

point

C

where

the

trolley

velocity

is

zero.

As

the

trolley

reaches

point

B

its

velocity

is

then

atmaximumnegative

and

the

force

is

zero.

The

force

then

starts

to

go

positive

to

retard

the

trolley

to

zero

velocity

atpoint

A

where

the

force

is

again

at

amaximum.Because

the

current

lags

behind

the

voltage

and

the

voltage

is

only

at

its

peak

for

an

instant,

maximumcurrent

equivalent

to

ad.c.

circuit

will

never

bedeveloped.

In

fact

the

higher

the

frequency

of

the

a.c.

source

voltage

the

less

time

the

current

has

to

grow.

For

an

inductor

as

frequency

increases

so

currentdecreases.電感(機(jī)械比喻)作用在小車上的變力，使它在A與C點(diǎn)之間往復(fù)運(yùn)動(dòng)A點(diǎn)時(shí)，作用力最大B點(diǎn)時(shí)減為零，然后反向增加，C點(diǎn)時(shí)為最大反向作用力B點(diǎn)時(shí)又減為零，然后正向增加，A點(diǎn)時(shí)為最大正向作用力MACFB作用力/電壓慣性/電感電磁場(chǎng)B

A

B

C

B

A

B

C

B速度/電流CapacitanceA

capacitor

is

a

device

that

can

accumulate

andstore

a

charge.

It

consists

of

two

metal

plates

close

together

butinsulatedfromeach

other.

When

a

potential

difference

is

placedacross

a

capacitor

one

plate

will

charge

positively

and

the

other

negatively.

During

this

shortprocess

current

will

appear

to

flow

butonce

the

plates

are

charged

there

will

be

no

current

flow

because

this

is

prevented

by

the

insulationThe

unit

of

capacitance

is

the

Farad

F.One

Farad

is

quite

large

by

electronic

component

standards

and

smaller

values

will

most

often

be

encountered1,000,000

microfarads(礔)=1F1,000,000,000

nanofarads

(nF)

=

1F1,000,000,000,000

picofarads

(pF)

=

1FElectrolytic

capacitors

are

polarity

sensitive

an

will

be

marked

at

the

ends.

If

one

is

inadvertentlyreverse

connected

anembarrassingexplosion

willresult.Other

types

unless

marked

can

be

connected

either

way

round.電容電容的單位是法拉

F一法拉是一個(gè)頗大的單位，我們常用較小的單位1,000,000微法(礔)=1F1,000,000,000毫微法

(nF)=1F1,000,000,000,000皮法(pF)=1F電容表示充電量電容器的元件符號(hào)電解電容

(有極性)+-If

a

capacitor

is

connected

in

ad.c

circuit

the

behaviour

of

the

voltage

across

the

capacitor

and

current

flowing

in

the

circuit

will

be

as

shown.

At

the

instant

ofswitch

on

the

rate

of

change

of

potential

difference

across

the

capacitor

will

be

at

a

maximum,

thesteepest

part

of

the

curve,

therefore

this

will

be

the

instant

of

maximumcurrent

flowing

in

the

circuit.

As

the

capacitor

charges

and

the

rate

of

voltage

rise

becomesless,

so

the

current

flowing

falls

until

the

capacitor

is

fully

charged

and

current

flow

halts.Once

charged

at

aparticular

voltageacapacitor

will

block

d.c.

but

if

there

is

anychange

to

the

voltage,

higher

or

lower,

there

will

be

corresponding

currentflow

until

the

d.c.

voltage

has

stabilised.電容(直流d.c.電路)這個(gè)電路中，由于電容器充電，恒定電壓產(chǎn)生的最大電流，會(huì)快速降至零因?yàn)檫@個(gè)電路沒(méi)有電阻，開(kāi)關(guān)合上時(shí)等于短路電容器截止直流電時(shí)間V(通過(guò)電容器)電流In

this

analogy,

the

behaviour

of

acapacitor

can

be

likened

toahydraulic

cylinder

with

a

spring

centred

piston.

If

a

d.c.

hydraulic

source

were

applied

to

theleft

hand

end

of

the

hydraulic

capacitor,

the

piston

would

be

pushed

to

the

right

and

oil

would

flow

out

of

the

right

hand

portat

the

same

rate

as

it

enters

the

left.

At

first

it

will

be

fast

because

the

opposition

from

the

spring

will

be

weak,

then

slowing

up

as

the

spring

is

compressed.

When

the

spring

balances

thepressure

the

capacitor

is

fully

charged

for

that

pressure

and

there

is

no

flow.

If

the

pressure

changes

slightly

the

position

of

the

piston

will

change

and

there

willbe

some

flow

while

this

is

happening.電容(直流d.c.電路)(機(jī)械比喻)一個(gè)電容器就象一個(gè)液壓儲(chǔ)油器，活塞被彈簧定位在中間一個(gè)恒定液壓源推動(dòng)活塞，直至壓力被彈簧力平衡這與通過(guò)電容器的電流相似，起先快，然后慢到停下In

this

analogy,

the

behaviour

of

acapacitor

can

be

likened

toahydraulic

cylinder

with

a

spring

centred

piston.

If

a

d.c.

hydraulic

source

were

applied

to

theleft

hand

end

of

the

hydraulic

capacitor,

the

piston

would

be

pushed

to

the

right

and

oil

would

flow

out

of

the

right

hand

portat

the

same

rate

as

it

enters

the

left.

At

first

it

will

be

fast

because

the

opposition

from

the

spring

will

be

weak,

then

slowing

up

as

the

spring

is

compressed.

When

the

spring

balances

thepressure

the

capacitor

is

fully

charged

for

that

pressure

and

there

is

no

flow.

If

the

pressure

changes

slightly

the

position

of

the

piston

will

change

and

there

willbe

some

flow

while

this

is

happening.電容(直流d.c.電路)(機(jī)械比喻)一個(gè)電容器就象一個(gè)液壓儲(chǔ)油器，活塞被彈簧定位在中間一個(gè)恒定液壓源推動(dòng)活塞，直至壓力被彈簧力平衡這與通過(guò)電容器的電流相似，起先快，然后慢到停下In

this

analogy,

the

behaviourof

a

capacitor

can

be

likened

to

a

hydraulic

reservoir

with

aspring

centred

piston.

If

ad.c.

hydraulic

source

were

applied

to

theleft

hand

end

of

the

hydraulic

capacitor,

the

piston

would

be

pushed

to

the

right

and

oil

would

flow

out

of

the

right

hand

portat

the

same

rate

as

it

enters

theleft.

At

first

it

will

be

fast

because

the

opposition

from

the

spring

will

be

weak,

then

slowing

up

as

the

spring

is

compressed.

When

the

spring

balances

thepressure

the

capacitor

is

fully

charged

to

that

pressure

and

there

is

no

flow.

If

the

pressure

changes

slightly

the

position

of

the

piston

will

change

and

there

willbe

some

flow

while

this

is

happening.電容(直流d.c.電路)(機(jī)械比喻)不象一個(gè)裝有彈簧的液壓儲(chǔ)油器，如果開(kāi)路，電容器不會(huì)失去電量電容器充得的電壓等于提供的電壓充電量由電容器的規(guī)格決定For

apurely

capacitive

a.c.

circuit

the

current

will

also

be

atits

highest

whenthe

rate

of

change

of

voltage

is

atits

steepest.

At

the

instant

of

peak

voltage

thereis

no

rate

of

change

and

so

the

current

passes

through

zero.

The

current

leads

the

voltage

by

90o.In

an

a.c.

circuit

the

voltage

is

changing

ata

controlled

rate

but

this

rate

is

governed

by

the

frequency

of

the

a.c.

signal.

Therefore

the

higher

this

frequency

thegreater

will

be

the

current

flowing

in

the

circuit.電容(交流a.c.電路)這個(gè)電路中，電流隨電壓變化率而相似地改變電壓曲線到達(dá)急彎時(shí)，電流最大到頂點(diǎn)時(shí)，電壓變化率為零，所以電流為零電容器可以通過(guò)交流電純電容式電路電流電壓電流超前電壓90oUsing

our

hydraulic

capacitor

analogy,

if

an

a.c.

hydraulic

source

were

applied

to

the

left

hand

end

of

the

hydraulic

capacitor,

the

piston

will

first

move

acertain

distance

to

the

right

and

then

be

drawn

back

throughthe

centre

to

an

equal

and

opposite

distance

to

the

left.

For

both

positive

and

negative

parts

of

thecycle

the

distance

is

the

point

at

which

the

spring

force

balances

the

positive

and

negative

peak

pressures.

If

for

this

partof

the

explanation

we

disregard

theeffects

of

inertia

of

the

piston,

spring

and

oil,

the

displacement

for

aparticular

peak

to

peak

pressure

will

be

the

same

even

if

the

frequency

were

to

rise.Therefore

the

flow

will

increase

as

the

frequency

increases.The

size

of

a

capacitor

also

influences

the

flow

of

current

the

larger

the

capacitor

the

higher

the

current電容(交流a.c.電路)(機(jī)械比喻)假想一個(gè)交變液壓源，加在液壓儲(chǔ)油罐的左端活塞移向右面，然后又被拉回左面，并按輸入變化連續(xù)地作往復(fù)運(yùn)動(dòng)右端的“出”和“入”流量將跟隨左端的“入”和“出”Using

our

hydraulic

capacitor

analogy,

if

an

a.c.

hydraulic

source

were

applied

to

the

left

hand

end

of

the

hydraulic

capacitor,

the

piston

will

first

move

acertain

distance

to

the

right

and

then

be

drawn

back

throughthe

centre

to

an

equal

and

opposite

distance

to

the

left.

For

both

positive

and

negative

parts

of

thecycle

the

distance

is

the

point

at

which

the

spring

force

balances

the

positive

and

negative

peak

pressures.

If

for

this

partof

the

explanation

we

disregard

theeffects

of

inertia

of

the

piston,

spring

and

oil,

the

displacement

for

aparticular

peak

to

peak

pressure

will

be

the

same

even

if

the

frequency

were

to

rise.Therefore

the

flow

will

increase

as

the

frequency

increases.The

size

of

a

capacitor

also

influences

the

flow

of

current

the

larger

the

capacitor

the

higher

the

current電容(交流a.c.電路)(機(jī)械比喻)假想一個(gè)交變液壓源，加在液壓儲(chǔ)油罐的左端活塞移向右面，然后又被拉回左面，并按輸入變化連續(xù)地作往復(fù)運(yùn)動(dòng)右端的“出”和“入”流量將跟隨左端的“入”和“出”Using

our

hydraulic

capacitor

analogy,

if

an

a.c.

hydraulic

source

were

applied

to

the

left

hand

end

of

the

hydraulic

capacitor,

the

piston

will

first

move

acertain

distance

to

the

right

and

then

be

drawn

back

throughthe

centre

to

an

equal

and

opposite

distance

to

the

left.

For

both

positive

and

negative

parts

of

thecycle

the

distance

is

the

point

at

which

the

spring

force

balances

the

positive

and

negative

peak

pressures.

If

for

this

partof

the

explanation

we

disregard

theeffects

of

inertia

of

the

piston,

spring

and

oil,

the

displacement

for

aparticular

peak

to

peak

pressure

will

be

the

same

even

if

the

frequency

were

to

rise.Therefore

the

flow

will

increase

as

the

frequency

increases.The

size

of

a

capacitor

also

influences

the

flow

of

current

the

larger

the

capacitor

the

higher

the

current電容(交流a.c.電路)(機(jī)械比喻)假想一個(gè)交變液壓源，加在液壓儲(chǔ)油罐的左端活塞移向右面，然后又被拉回左面，并按輸入變化連續(xù)地作往復(fù)運(yùn)動(dòng)右端的“出”和“入”流量將跟隨左端的“入”和“出”As

we

have

seenwhenstudyinginductors,

as

the

frequency

increases

so

the

current

decreases

but

with

a90o

lag.

The

inductor

behaves

likearesistor

that

isfrequency

dependant.

This

equivalent

resistance

is

called

reactance.

For

any

specific

frequency

thereactance

can

be

given

an

equivalent

resistive

value

in

ohms.電抗(電感式)電源頻率增加，電流減小電感器相當(dāng)于一個(gè)電阻，但它與頻率有關(guān)這個(gè)等效電阻稱為感抗任何一個(gè)頻率，感抗都有一個(gè)相對(duì)的電阻值(歐姆)電壓均方根值90°滯后純電感電路中的交流電VI感抗ZZ

=I

均方根值V

均方根值歐姆電流均方根值Similarly

withcapacitors,

they

also

have

reactance

to

a

changingsignal

voltage

but

the

effect

is

the

other

way

round.

The

higher

the

frequency

of

the

signal

thehigher

the

current

but

with

a

90o

lead.

Againfor

any

specific

frequency

the

reactance

can

be

given

an

equivalent

value

in

ohms.電抗(電容式)當(dāng)電壓變化時(shí)，電容器也有電抗，但效應(yīng)的形式不同信號(hào)的頻率越高，電流越大，并超前90o任何一個(gè)頻率，容抗都有一個(gè)相對(duì)的電阻值(歐姆)電壓均方根值電流均方根值90

°超前純電容電路中的交流電容抗ZI

均方根值V

均方根值Z=

歐姆電阻電路中也有純電阻部分，這里電流與電壓的相位相同純電阻電路中的交流電阻抗R電壓均方根值電流均方根值R

=V

均方根值I

均方根值歐姆Impedance

is

often

a

misused

or

unqualified

term.

Impedance

is

the

equivalent

resistance

in

ohmsof

an

output

or

input

circuit

that

gives

orrequires

a

signalwhere

the

voltage

is

oscillatingata

specific

freque