Bài 3:

a. \(R=p\dfrac{l}{S}=1,1.10^{-6}\dfrac{30}{0,2.10^{-6}}=165\Omega\)

b. \(Q=UIt=220\left(\dfrac{220}{165}\right).15.60=254000\left(J\right)\)

Bài 2:

a. \(R=\dfrac{U^2}{P}=\dfrac{220^2}{1000}=48,4\Omega\)

b. \(Q=UIt=220\left(\dfrac{220}{48,4}\right).4.3600=14400000\left(J\right)\)

c. \(Q'=Q.40=14400000.40=576000000\left(J\right)=120000\)kWh

\(\Rightarrow T=Q'.2100=120000.2100=252000000\left(dong\right)\)

Bài 1:

a. \(Q=UIt=220.2,5.1=550\left(J\right)\)

b. \(\left\{{}\begin{matrix}Q_{thu}=mc\left(t-t_1\right)=2.4200\left(100-20\right)=672000\left(J\right)\\Q_{toa}=UIt=220.2,5.15.60=495000\left(J\right)\end{matrix}\right.\)

\(\Rightarrow H=\dfrac{Q_{toa}}{Q_{thu}}100\%=\dfrac{495000}{672000}100\%\approx73,6\%\)

nếu lm đc thì lm cả bài 3,4 nha.mik tick cho!

1 C => teacher's

2 C => its

3 D => bỏ

4 A => is

5 A => is

1 C -> teacher's

2 C -> Its

3 D -> bỏ

4 A -> is

5 A -> is

1. teacher=> teacher's

2. name's => name's is

3. near to=> near (bỏ to)

4. are=> is

5. are=> is

IV

1 by

2 on

3 at - in

4 to

5 for

6 with

7 into

8 of

9 in

V

1 carelessly

2 increasingly

3 protection

4 unresonable

5 preservation

1 to go => go

2 is => was

3 living=> lived

4 by => on

5 smoking => smoked

6 than => as

7 since => for

8 much => more

9 keeping => kept

10 mine => from mine

1. C

2. A

3. B

1. C

2. A

3. B

1. C

2. A

3. B

1 B => worrried 

2 B => didn't 

3 B => play

4 A => many

5 C => to

1 B => worrried 

2 B => didn't 

3 B => play

4 A => many

5 C => to

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