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Concours: Gagne à utiliser Alloprof cet été

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Secondaire 5 • 1a

Hi, I’m trying to do this but the steps dont seem right, and I’m not sure what formula to use. Do i use P=E/Time? If so, how do I know what the Power is?



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Explications (1)

  • Explication d'Alloprof

    Explication d'Alloprof

    Cette explication a été donnée par un membre de l'équipe d'Alloprof.

    Équipe Alloprof • 1a

    Thank you for your question!

    Yes, P=E/time is a formula you could use to solve this problem. However, you will also need to use...

    $$ P = U•I $$

    Legend :

    • P : power (W)
    • U : voltage (V)
    • I : amperage (I)

    ...and also...

    $$$ 1\:W•1\:h = 3600\:J $$

    ...and finally...:

    $$ Q = mc∆T $$

    Legend :

    • Q : energy (J)
    • m : mass (g)
    • c : specific heat capacity (J/(g•°C))
    • ∆T : temperature variation (°C)

    Therefore, the solution to the problem should look like this :

    1. First, find the power of the hot plate using P=UI. Don't forget to multiply the end result to take into account its energetic efficiency.
    2. Next, find the energy required to bring the water to boiling point using Q = mc∆T. You may have to look around to find the quantity of water being boiled as well as its initial temperature. Remember that, for water, 1 mL = 1 g. The final value of Q is the same variable as E.
    3. Finally, use P = E/t to determine the amount of time required to boil the water. Be careful to remember that 1 W = 1 h • 3600 J.

    Don't hesitate to ask for more help!

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