Một bếp điện đun hai lít nước ở nhiệt độ t1 = 20oC. Muốn đun sôi lượng nước đó trong 20 phút thì bếp điện phải có công suất là bao nhiêu ? Biết nhiệt dung riêng của nước c = 4,18 kJ/(kg.K) và hiệu suất của bếp điện H = 70%.

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Một số câu hỏi khác có thể bạn quan tâm.

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

   November 7, 2006 / Vietnam became WTO’s 150^th member / after several years of preparation and negotiation.
  
  

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

  Government figures / GDP growth / 8.17% / 2006.
  
  

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

  Vietnam’s Minister of Planning and Investment / the government / target / a GDP growth of around 8.5% / 2007.
  
  

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

  Imagine an entirely wireless world where the Net is "always on, always there", we live in endless sea of data, and objects are alive with intelligent.

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

  Electricity is the most critical energy for the future of many countries and cheap, plentiful electricity is associated for high employment and productivity.

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

  Our continuously economic growth, the maintenance of our quality of life, and assurance of our security all depend on a abundant, affordable supply of electricity.

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

  future                  mature                    pasture                 nature

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

  chore            technology                much                  exchange

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

  threaten                earth                   healthy                 breathe

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

  wipe             allow                  powerful                  answer