His drawings are very good. He’ll be a famous (art) _____________ one day.

arter

arting

artist

arted

You can (find) _____________ math books on the racks in the middle.

find

finds

is finding

will find

What a (bore) _____________ party!

bored

boring

unbored

bore

The company has only 70 (employ) _____________

employer

employ

employed

employees

There isn’t _____________ bread in the cupboard.

some

of

any

no

_____________ will we meet? – In front of the movie theater.

When

Why

Where

What

The weather today is much _____________ than yesterday.

good

best

better

gooder

What classes _____________ you (have) _____________ today?

does / have

do/has

do/have

does/has

What _____________ she (study) _____________ now?

are/studying

is/studying

do/study

does/study

Câu 1 bị dư 1 chữ am nhé!

\(\left\{{}\begin{matrix}Q=UIt\\Q=\dfrac{U^2t}{R}\\Q=I^2Rt\end{matrix}\right.\)

Chọn A

a. \(R=\dfrac{U}{I}=\dfrac{3,5}{2,5}=1,4\Omega\)

b. \(R=p\dfrac{l}{S}\Rightarrow S=\dfrac{l.p}{R}=\dfrac{10.2,8.10^{-8}}{1,4}=2.10^{-7}\Omega m\)

\(\left\{{}\begin{matrix}v'=s':t'=50:3=\dfrac{50}{3}\left(\dfrac{km}{h}\right)\\v''=s'':t''=35:\left(\dfrac{20}{60}\right)=105\left(\dfrac{km}{h}\right)\\v=\dfrac{s'+s''}{t'+t''}=\dfrac{50+35}{3+\left(\dfrac{20}{60}\right)}=25,5\left(\dfrac{km}{h}\right)\end{matrix}\right.\)

Bài 2:

a. \(R=\dfrac{R1.R2}{R1+R2}=\dfrac{20.30}{20+30}=12\Omega\)

\(U=U1=U2=IR=12.2=24V\left(R1\backslash\backslash\mathbb{R}2\right)\)

b. \(\left\{{}\begin{matrix}I1=U1:R1=24:20=1,2A\\I2=U2:R2=24:30=0,8A\end{matrix}\right.\)

c. \(I=I12=I3=0,5A\left(R12ntR3\right)\)

\(U3=U-U12=24-\left(0,5.12\right)=18V\)

d. \(P=UI'=24.0,5=12\)W