Electrician Lao Li urgently needs one 30 ohm resistor and one 5 ohm resistor when repairing electrical appliances, but he only has five 10 ohm resistors on hand. Please find a way to help Lao Li solve the problem immediately: ()

You can think of it as doubling the cross-sectional area. The larger the cross-sectional area, the smaller the resistance. Do you know this? Use three 10 ohm resistors in series. This will become 30 ohm. That is to increase the length. This is very simple. If you don't know

Resources and evaluation (people's Education Press) Ohm's law of physics and its application (Heilongjiang Education Press) P26
A 20 Ω resistor is connected in parallel with a sliding rheostat marked "60 Ω, 1A". When the slide of the sliding rheostat moves, the total resistance in the circuit will change, and the change range of the total resistance is ()
A. Between 20 Ω and 60 Ω
B. Between 15 Ω and 20 Ω
C. Between 0 Ω and 15 Ω
D. Between 0 Ω and 20 Ω
Please explain the reason! Thank you

The answer is C~

A problem of filling in the blanks in Physics (about Ohm's law)
In a series circuit (lamp L, resistor R, sliding rheostat R '), the resistance value of L is 12 Ω, and the power supply voltage is 8 v. in order to make sliding rheostat slide P in sliding, the maximum voltage added to the lamp is 6 V, and the minimum voltage is 3 V, then the resistance value of resistor R is 0__ What is the maximum resistance of the sliding rheostat R '_ Oh

When the voltage is up to 6V,
The voltage at R is 2V
Current I = 6 / 12 = 0.5A,
The resistance of R is r = 2 / 0.5 = 4 ohm
When the minimum voltage is 3V,
At this time, the current I1 = 3 / 12 = 0.25A
The total resistance of R and R 'is r = 5 / 0.25 = 20 ohm
So the maximum resistance of R 'is 20-4 = 16 ohm

Please give an example of a pair of reciprocal propositions

If a + B & gt; 0, then a & gt; 0, B & gt; 0, if two lines are parallel, the angles with the same angle are all right angles

In △ ABC, if three sides are known to be continuous positive integers, the maximum angle is obtuse
Write a general term formula of the following sequence so that the first four terms are the following numbers
(1) Three in two, five in four, seven in eight, nine in sixteen;
（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）9,99,999,9999

（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

Irregular past tense of verbs in junior high school English
Junior high school's is good, want original form and past tense,

(1) AAA type (verb prototype, past tense, past participle homograph)
Cost cost
Cut cut
Hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit hit
Hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt hurt
Let let
Put put put
Read read
Spread (spread / spread)
spread spread
(2) AAB (the original form of the verb is the same as the past tense)
Beat beat
(3) ABA type (the original form of the verb is the same as the past participle)
Became became
Come come come
Run ran run
(4) ABB type (past tense and past participle in the same form)
Dig dig
Get got got
Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang
Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang Hang
Hold hold hold
Lay lay
Shine shine shine
Sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit sit
Win won
Met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met met
Keep keep keep
Sleep sleep
Sweep sweep sweep
Feel feel
Flee fled fled
Smile
Leave left
Build build
Lent lent
Send send
Spend spend
Sink / sink / sink / sink
Lose lost
Burn burn
Learning learning
Mean mean
Catch catch
Teach
Bring about
Fight fought
Buy buy
Think think think
Hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear hear
Sell sold sold
Tell told told
Say say say
Find found
Feed feed
Have / have had
Make make make
Stand stock
Smile / Smile / smile
Stick stick
Spell / spelled spell / spelled
Spit spat
Understand understand understand understand
(5) ABC type (the original form of verb, past tense and past participle)
Begin began begun
Drink drink
Hid hidden
Ring ring
Sing sang sung
Swim swim
Blow blow
Draw draw
Fly flow
Grow great grow
Know know know
Throw throw
Show shown
Break break break
Choose choose
Forget forget forget forget
Freeze freeze
Speak speak speak
Wake up
Drive drive
Eat eat eat
Fall fall
Give, give, give
Rose risen
Take take
Mistake mistook mistaken
Ride ride ride
Write write
Do do
Go went gone
Lie lay lain
See see see
Wear
Be (am, is, are)
The past tense and past participle of irregular verbs
1、 Words with the same form and pronunciation of the original form, past tense and past participle usually end with T or D
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
Special: Although the past tense and past participle of the verb read are the same as the original form, read read, but the pronunciation is [RI: D], [red], [red]
2、 The past participle of some verbs is the same as the original form
come-came-come, become-became-become, run-ran-run, overcome-overcame-overcome
3、 The past tense of some verbs is the same as the past participle
1. Change the letter D at the end of the word to t
lend-lent-lent, spend-spent-spent, send-sent-sent
2. Change the middle vowel of a word
sit-sat-sat, win-won-won, shine-shone-shone, hold-held-held
3. For verbs ending in eep, change eep to ept
keep-kept-kept, sleep-slept-slept, sweep-swept-swept
4. Verbs that both the past tense and the past participle end with "enough" or "enough"
buy-bought-bought, fight-fought-fought, think-thought-thought, bring-brought-brought, teach-taught-taught, catch-caught-caught
5. Some verbs ending with ay change ay into aid in the past tense and past participle
say-said-said, lay-laid-laid, pay-paid-paid
6. There are some other forms of changes, such as:
have-had-had, learn-learnt-learnt, leave-left-left, lose-lost-lost, make-made-made, meet-met-met, feel-felt-felt
4、 Some verbs contain the letter I in the original form, which changes into a in the past tense and u in the past participle
begin-began-begun, sing-sang-sung
5、 When a verb ends with the letter ow or aw, it usually changes the vowel into e when it becomes a past tense. When it becomes a past participle, it usually only adds n at the end of the word
blow- blew- blown, draw-drew-drawn, grow-grew-grown, throw-threw-thrown, know-knew-known
6、 The past participle of some verbs is to add n or en at the end of the original form to become a word ending with en
Rise-rose-risen, arise-arose-arisen, give-gave-given, take-took-taken, fall-fell-fallen, drive-drove-driven, eat-ate -eaten
Special: write write write, speak spoke spoke spoke spoke, ride ride ride ridden, get got got got got
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
I went to gxenglish
Irregular verb list (for junior high school students)
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

Electrician Lao Li urgently needs one 30 ohm resistor and one 5 ohm resistor when repairing electrical appliances, but he only has five 10 ohm resistors on hand. Please find a way to help Lao Li solve the problem immediately: ()