電工老李修理電器時急需30歐姆和5歐姆電阻各一個，但手邊只有10歐姆的電阻5個，請你想辦法幫助老李馬上解决問題：（）

電工老李修理電器時急需30歐姆和5歐姆電阻各一個，但手邊只有10歐姆的電阻5個，請你想辦法幫助老李馬上解决問題：（）

兩個五歐姆的一並聯就成了五歐姆的了.你可以把它看成是新增了一倍的橫截面積.橫截面積越大電阻越小你這種事知道咯？用三個十歐姆的電阻串聯.這樣就成了三十歐姆的了.那就是新增了長度咯.這個很簡單.要是不知道的話.把…

初二下資源與評估（人教版）物理歐姆定律及其應用（黑龍江教育出版社）P26頁第八題選擇
一隻20Ω的電阻器與一個標有“60Ω，1A”字樣的滑動變阻器並聯.滑動變阻器的滑片移動時，電路中的總電阻會發生變化，則總電阻的變化範圍是（）
A.20Ω與60Ω之間
B.15Ω與20Ω之間
C.0Ω與15Ω之間
D.0Ω與20Ω之間
請說明原因！謝謝

答案是C~

一道物理填空題（關於歐姆定律）
在一個串聯電路中（燈L、電阻R、滑動變阻器R'），等L的電阻值為12歐，電源電壓為8伏.要想使滑動變阻器滑片P在滑動中，加在電燈上的電壓最大是6伏，最小是3伏，那麼電阻R的電阻值是____歐，滑動變阻器R'的最大阻值是___歐.

當電壓為最大6V時，
R上的電壓是2V.
電流I=6/12=0.5A，
R的電阻為R=2/0.5=4歐.
當最小為3V時，
此時電流I1=3/12= 0.25A.
R和R'的總電阻為R總=5/0.25=20歐
所以R'的最大電阻為20-4=16歐

請舉出一對互逆命題的例子

“兩直線平行，內錯角相等”“內錯角相等，兩直線平行直角都相等同位角相等，兩直線平行如果a+b>；0，那麼a>；0，b>；0兩直線平行，同位角相等相等的角都是直角

△abc中，若已知三邊為連續正整數，最大角為鈍角
寫出下麵數列的一個通項公式，使它的前4項分別是下列各數.
（1）二分之三，四分之五，八分之七，十六分之九；
（2）-（3×7），（4×8），-（5×9），（6×10）；
（3）3,5,9,17；
（4）1，½；，3，¼；
（5）0，（2²；-2）/5，（3²；-3）/10，（4²；-4）/7
（6）9,999999999

（1）：（2n+1）/（2^n）
（2）：（n+2）*（n+6）*（-1）^n
（3）：2^n+1
（4）n^[（-1）^（n+1）]
（5）（n^n-n）/（n^2+1）
（6）10^n-1

初中英語動詞不規則過去式錶
國中的就好了，要原形和過去式，

（1）AAA型（動詞原形、過去式、過去分詞同形）
cost（花費）cost cost
cut（割）cut cut
hit（打）hit hit
hurt傷害）hurt hurt
let（讓）let let
put（放）put put
read（讀）read read
spread（伸展/傳播）
spread spread
（2）AAB型（動詞原形與過去式同形）
beat（跳動）beat beaten
（3）ABA型（動詞原形與過去分詞同形）
become（變成）became become
come（來）came come
run（跑）ran run
（4）ABB型（過去式與過去分詞同形）
dig（挖）dug dug
get（得到）got got
hang（吊死）hanged hanged
hang（懸掛）hung hung
hold（抓住）held held
lay（產卵）laid laid
shine（照耀）shone shone
sit（坐）sat sat
win（贏）won won
meet（遇見）met met
keep（保持）kept kept
sleep（睡）slept slept
sweep（掃）swept swept
feel（感覺）felt felt
flee（逃跑）fled fled
smell（聞）smelt smelt
leave（離開）left left
build（建設）built built
lend（借出）lent lent
send（傳送）sent sent
spend（花費）spent spent
sink（沉下）sunk /sank snuk /sunken
lose（遺失）lost lost
burn（燃燒）burnt burnt
learn（學習）learnt learnt
mean（意思是）meant meant
catch（抓住）caught caught
teach（教）taught taught
bring（帶來）brought brought
fight（戰鬥）fought fought
buy（買）bought bought
think（想）thought thought
hear（聽見）heard heard
sell（賣）sold sold
tell（告訴）told told
say（說）said said
find（找到）found found
feed（飼養）fed fed
have/has（有）had had
make（製造）made made
stand（站）stood stood
smell（聞）smelled /smelt smelled /smelt
stick（粘貼/刺）stuck stuck
spell（拼寫）spelt/spelled spelt/spelled
spit（吐唾沫）spat spat
understand（明白）understood understood
（5）ABC型（動詞原形、過去式與過去分詞三者不同形）
begin（開始）began begun
drink（喝）drank drunk
hide（躲藏）hid hidden
ring（鈴響）rang rung
sing（唱）sang sung
swim（游泳）swam swum
blow（吹）blew blown
draw（畫）drew drawn
fly（飛）flew flown
grow（生長）grew grown
know（知道）knew known
throw（投擲）threw thrown
show（出示）showed shown
break（打破）broke broken
choose（選擇）chose chosen
forget（忘記）forgot forgotten（forgot）
freeze（結冰／凝固）froze frozen
speak（說）spoke spoken
wake（醒）woke woke
drive（駕駛）drove driven
eat（吃）ate eaten
fall（落下）fell fallen
give（給）gave given
rise（升高）rose risen
take（取）took taken
mistake（弄錯）mistook mistaken
ride（騎）rode ridden
write（寫）wrote written
do（做）did done
go（去）went gone
lie（平躺）lay lain
see（看見）saw seen
wear（穿）wore worn
be（am，is，are）（是）was，were been
不規則動詞過去式和過去分詞巧記方法
一、原形、過去式和過去分詞的詞形和讀音都相同的單詞，結尾字母一般是t或d.如：
cut-cut-cut，hit-hit-hit，put-put-put，cost-cost-cost，let-let-let，shut-shut-shut，set-set-set，hurt-hurt-hurt，spread-spread-spread
特殊：動詞read的過去式和過去分詞雖然詞形與原形一致，read-read-read，但發音分別是[ri:d]-[red]-[red].
二、有些動詞的過去分詞與原形是一樣的.如：
come-came-come，become-became-become，run-ran-run，overcome-overcame-overcome
三、有些動詞的過去式和過去分詞相同.如：
1.把單詞結尾的字母d改為t.如：
lend-lent-lent，spend-spent-spent，send-sent-sent
2.改變單詞中間母音字母.如：
sit-sat-sat，win-won-won，shine-shone-shone，hold-held-held
3.以eep結尾的動詞，把eep改為ept.如：
keep-kept-kept，sleep-slept-slept，sweep-swept-swept
4.過去式和過去分詞都以augh或ough結尾的動詞.如：
buy-bought-bought，fight-fought-fought，think-thought-thought，bring-brought-brought，teach-taught-taught，catch-caught-caught
5.有的以ay結尾的動詞，在過去式和過去分詞中把ay變成aid.如：
say-said-said，lay-laid-laid，pay-paid-paid
6.另有一些其它形式的變化.如：
have-had-had，learn-learnt-learnt，leave-left-left，lose-lost-lost，make-made-made，meet-met-met，feel-felt-felt
四、有些動詞原形中含有字母i，在過去式中變i為a，在過去分詞中變i為u.如：
begin-began-begun，sing-sang-sung
五、以字母ow或aw結尾的動詞，在變成過去式時，通常把母音字母變成e，在變成過去分詞時，通常只在詞尾加n.如：
blow- blew- blown，draw-drew-drawn，grow-grew-grown，throw-threw-thrown，know-knew-known
六、有些動詞的過去分詞是在原形詞尾加n或en，變成以en結尾的單詞.如：
Rise-rose-risen，arise-arose-arisen，give-gave-given，take-took-taken，fall-fell-fallen，drive-drove-driven，eat-ate -eaten
特殊：write-wrote-written，speak-spoke-spoken，ride-rode-ridden，get-got-gotten
1. cut cut cut
2. hit hit hit
3. let let let
4. put put put
5. cost cost cost
6. hurt hurt hurt
7. read read read
A B B
1. lend lent lent
2. spend pent spent
3. build built built
4. sleep slept slept
5. keep kept kept
6. leave left left
7. feel felt felt
8. lose lost lost
9. sit sat sat
10. meet met met
11. tell told told
12. sell sold sold
13. hold held held
14. make made made
15. find found found
16. have had had
17. say said said
18. stand stood stood
19. hear heard heard
20. mean meant meant
21. win won won
22. bring brought brought
23. buy bought bought
24. think thought thought
25. teach taught taught
26. catch caught caught
A B A
1. run ran run
2. come came come
3. become became become
A B C
1. grow grew grown
2. know knew known
3. throw threw thrown
4. blow blew blown
5. draw drew drawn
6. drive drove driven
7. wake woke woken
8. give gave given
9. take took taken
10. mistake mistook mistaken
11. see saw seen
12. write wrote written
13. ride rode ridden
14. eat ate eaten
15. fall fell fallen
16. break broke broken
17. choose chose chosen
18. speak spoke spoken
19. forget forgot forgotten
20. do did done
21. go went gone
我上gxenglish的
不規則動詞錶（初中生用）
Infinitive Past tense Past participle
be
am，is was been
are were been
become became become
begin began begun
break broke broken
bring brought brought
build built built
burn burned/burnt burned/burnt
buy bought bought
can could—
catch caught caught
choose chose chosen
come came come
cost cost cost
cut cut cut
do did done
draw drew drawn
dream dreamed/dreamt dreamed/dreamt
drink drank drunk
drive drove driven
eat ate eaten
fall fell fallen
feel felt felt
fight fought fought
find found found
fly flew flown
forget forgot forgotten
get got got
give gave given
go went gone
grow grew grown
have/has had had
hear h