Tính điện trở tương đương của 100 điện trở 1+1/2+1/3+.....+1/100 mắc song song.

2 câu trả lời

Đáp án:

Gửi bạn đáp án

Giải thích các bước giải:

Công thức tính điện trở tương đương của 100 điện trở mắc // là:

$\frac{1}{R_{tđ}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}+...+\frac{1}{R_{100}}$

Thay số ta có:

$\frac{1}{R_{tđ}}=\frac{1}{1}+\frac{1}{1/2}+\frac{1}{1/3}+...+\frac{1}{1/100}

=1+2+3+...+100=5050$

Vậy $R_{tđ}=\frac{1}{5050}$ ohm

Đáp án: .

R=UI=150,5=30Ω

Mà : (R1ntR2)//R3

⇒R=R1R3+R2R3R1+R2+R3⇔30=1800+60R290+R2

⇔R2=30Ω R1ntR2

UAB=15V;R1=15Ω;R2=10Ω

I=?

U1=?;U2=?

BL :

Rtd=R1+R2=25Ω

I=UABRtd=0,6(A)

b) R3//R1

I=1A;R3=?

BL :

UAB=U3=15V

I3=1−0,6=0,4A

=>R3=150,4=37,5Ω

c) R3//R2

I=?

1Rtđ=1R2+1R3=119150=15019(Ω)

I=UABRTM=1515019=1,9(A)

Giải thích các bước giải: Khi đặt vào A và B hiệu điện thế UAB = 40V thì hiệu điện thế UCD=15V và dòng điện chạy qua R2 là I2=0,5A.

Khi đặt vào C và D hiệu điện thế U'CD=30V thì hiệu điện thế U'AB = 10V. Tính giá trị các điện tr

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EXERCISE 4: Mixed types Put the verb in the brackets in the correct form: Example: If I (have) ______have __time, I will write to him. 1. If it’s cold, I (need) ________________a heavier coat. 2. What are you going to do if you (have) ________________a holiday? 3. If I can go tomorrow, I (let) ________________you know. 4. If flowers don’t get any water, they (die) ________________ 5. I will go to the party unless it (rain) ________________. 6. If I got up earlier, I (not be) ________________late for work. 7. If I didn’t feel so tired, I (go) ________________.out with you. 8. If you (not pass) ________________the exam, would you take it again? 9. If I (be) ________________you, I would apply for the job. 10. I could repair the car if I (have) ________________the right tools. 11. If I (study) ________________hard, I would have passed the exam. 12. If I (not be) ________________busy yesterday, I would have visited you. 13. What would happen if you (not go) ________________to work tomorrow. 14. If I had gone to your party last night, I (be) ________________very tired. 15. You __________________________ (not be) angry if you had known the reason. 16. We’ll send for the doctor if he __________________________ (feel) worse. 17. Unless they turn the radio off, I __________________________ (go) somewhere else. 18. Unless it __________________________ (be) a nice day, we won’t go out. 19. The grass would look better if you __________________________ (take care) of it. 20. If you leave the gate open, people __________________________ (get in). 21. If you had asked her permission, she __________________________ (not let) you go. 22. If we leave before the breakfast, we __________________________(catch) the train. 23. If Tom _______________________ (ring), tell him I will phone him. 24. If I ______________________ (know) that you didn’t like fish, I wouldn’t have bought it. 25. I didn’t feel good yesterday. If I (feel) _____________better, I (come) ___________to class yesterday. 26. I (get) ______________you a present if I (know) _____________________it was your birthday yesterday. 27. If the weather (be) ______________________nice tomorrow, I (go) ______________________for a walk. 28. I don’t have enough time. If I (have) ______________enough time, I (go) ________________to the park. 29. I don’t understand that sentence. If I (understand) _________that sentence, I (explain) ________it to you. 30. If I (have) ____________________enough money last night, I (go) ______________________to see you. 31. What you (do) __________ if you (be) __________in my situation? 32. Their marriage only lasted three months. If he (be) __________less mean, she (not leave) _________him. 33. Good, everybody is ready. If we (leave) __________now, we (miss) __________the rush hour traffic. 34. If you (smoke) __________less you (have) __________much money. But I don’t think you ever will. 35. We have lost the camera. If we (lock) ________the car window, we (not give) ______them the opportunity to break in. 36. He threatens (resign) __________if we (not agree) __________to his proposal. 37. If you (press) __________this button, a receptionist (come) __________to help you. 38. If I (be) __________the Prime Minister, I (bring) __________back the capital punishment. 39. The only thing I haven’t got is a garden. If I (have) __________ one, I (grow) __________a lot of flowers. 40. If he (not start) __________at once, he (be) __________late for the train.

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