Câu 6:

\(U=I.R=10.1,5=15\left(V\right)\)

Câu 7:

\(P=U.I\Rightarrow U=\dfrac{P}{I}=\dfrac{10}{0,5}=20\left(V\right)\)

Câu 8:

\(R_{tđ}=\dfrac{R_1.R_2}{R_1+R_2}=\dfrac{10.30}{10+30}=7,5\left(\Omega\right)\)

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

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