Đặt điện áp V vào hai đầu đoạn mạch gồm biến trở R, cuộn cảm và tụ điện mắc nối tiếp. Khi R = 40 thì công suất tiêu thụ của mạch đạt giá trị cực đại P_m; khi R = thì công suất tiêu thụ của biến trở đạt cực đại. Giá trị của P_m là:  

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Một số câu hỏi khác có thể bạn quan tâm.

• Choose the best answer for the following sentence:

  He didn’t know what ___________ around him when he was sleeping.
  
  

• Choose the best answer for the following sentence:

  When he ___________ home he turned on the radio.
  
  

• Choose the best answer for the following sentence:

  ___________ do you prefer, Chemistry or Physics?

• Choose the best answer for the following sentence:

  The air-hostess had known that you were ill,_______________ ?

• Choose the best answer for the following sentence:

  I wish you ___________ her why we didn’t do our homework.
  
  

• Find a mistake in the four underlined parts of the sentence and correct it:

  After he finished writing the letter he went to post it immediately.

• Find a mistake in the four underlined parts of the sentence and correct it:

  Marie Curie was very poor, she had a little money to live on in Paris.

• Find a mistake in the four underlined parts of the sentence and correct it:

  Last night, before going to bed all the students watched a very interesting film.

• Choose the correct sentence which is built from the words and phrases given:

  Hillary Clinton / First Lady / the United States / 1993 / 20011 born / October 26, 1947 / Chicago, Illinois//.
  
  

• Choose the correct sentence which is built from the words and phrases given:

  Hillary Clinton's father / successful businessman/ the textile industry / her mother / homemaker //