Một khung dây tròn bán kính 4cm gồm 10 vòng dây. Dòng điện chạy trong mỗi vòng có cường độ 0,3A. Tính cảm ứng từ tại tâm của khung.

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Một số câu hỏi khác có thể bạn quan tâm.

• Choose a word that has different stress pattern:

  biodiversity                  personality                  familiarity                  opportunity

• Choose a word that has different stress pattern:

  entrapment                   encouragement                  ensure                   engineer

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

  Satellite photos provide a wide range of information, included water temperature.

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

  I wish you are here with me to enjoy our holiday.

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

  They were tired of their job; they should to change another that they really like.

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

  Sea turtles / turtles / find / all the world's oceans / except / Arctic Ocean //.
  
  

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

  Sea turtles / play / important roles / the ecosystems / the oceans / beaches//.
  
  

• Choose the word that has the underlined part pronounced differently from the rest:

  subtract                    doubt                    debt                     climb

• Choose the word that has the underlined part pronounced differently from the rest:

  product                 programme                     psychiatrist                    prefer

• Choose a word that has different stress pattern:

  forester                forename                    forget                     formal