The benefits that universities and colleges bring us many knowledges in our current life.First, we can increase our chances of getting a job. There are a lot of employers who ask for competent people, but they don't know who to hire to be the right fit. Having a university and college degree helps us to be trusted. Second, we can practice many skills in college. At university, you will have the opportunity to study and practice many soft skills such as negotiation, presentation, communication, teamwork,... Last, develop critical thinking. Critical thinking will follow you throughout your life and help you deal with work in a more objective, holistic way.After all, studying at the university is different from the subordinates, students have to study on their own. As a result, you will form the habit of self-study. What are you waiting for? Decide your favourite universities and colleges now.

Bạn tự vẽ sơ đồ mạch điện và tự làm tóm tắt nhé!
Bài 1:

b. \(U=IR=I\left(R1+R2\right)=0,4\left(15+2\right)=6,8\left(V\right)\)

c. \(I=I1=I2=\dfrac{U'}{R}=\dfrac{60}{15+2}=\dfrac{60}{17}\simeq3,5\left(A\right)\left(R1ntR2\right)\)

Bài 2:

\(5400kJ=1500\left(Wh\right)\)

a. \(A=Pt\Rightarrow P=\dfrac{A}{t}=\dfrac{1500}{1}=1500\left(W\right)\)

b. \(P=UI\Rightarrow I=\dfrac{P}{U}=\dfrac{1500}{220}=\dfrac{75}{11}\simeq6,82\left(A\right)\)

Bài 3:

a. \(R=p\dfrac{l}{S}=1,1.10^{-6}\dfrac{3}{0,05.10^{-6}}=66\left(\Omega\right)\)

b. \(P=UI=U\left(\dfrac{U}{R}\right)=220.\left(\dfrac{220}{66}\right)=733,33\left(W\right)\)

c. \(A=Pt=733,33.\left(\dfrac{30}{60}\right)=366,665\left(Wh\right)=0,366665\left(kWh\right)=1319994\left(J\right)\)

Bài 4:

a. \(S=\pi\dfrac{d^2}{4}=\pi\dfrac{1^2}{4}=0,785\left(mm^2\right)\)

\(\Rightarrow R=p\dfrac{l}{S}=5,5.10^{-8}\dfrac{10}{0,785.10^{-6}}=\dfrac{110}{157}\simeq0,7\left(\Omega\right)\)

b. \(A=Pt=UIt=U\left(\dfrac{U}{R}\right)t=70\left(\dfrac{70}{0,7}\right).\dfrac{1}{3}=2333,33\left(Wh\right)=2,33333\left(kWh\right)\simeq8400000\left(J\right)\)

 

 

1 C

2 C

3 C

4 C

5 A

6 B

7 A

11 

12 B

13 A

14 C

15D

4. B

5. A

6. C

7. C

8. B

9. B

10. A

11. C

12. 

13. A

14. 

15. C

Câu 3: 

c: Xét ΔAHB vuông tại H có HE là đường cao

nên \(AE\cdot AB=AH^2\left(1\right)\)

Xét ΔAHC vuông tại H có HF là đường cao

nên \(AF\cdot AC=AH^2\left(2\right)\)

Từ (1) và (2) suy ra \(AE\cdot AB=AF\cdot AC\)

\(Cau.23:\\ N=\left(A_1+T_1+G_1+X_1\right).2=\left(100+200=300+400\right).2=2000\left(Nu\right)\\ L=\dfrac{N}{2}.3,4=\dfrac{2000}{2}.3,4=3400\left(A^o\right)\\ Chon.C\)

Câu 20: C

Câu 21: B

🤔

🌚