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Measure the relation between the current of a circuit and the heating effect produced

  1. Mar 30, 2009 #1
    Hi everyone,

    I have an investigation to carry out for my Junior Certificate in Ireland. What I'm not sure about is the link between heat and temperature. I know that heat is energy, and temperature is the measurement of this energy, but I'm not sure what the link between celcius and joules is.

    1. Measure the relation between the current of a circuit and the heating effect produced by that circuit


    2. Joule's Law - W = (I^2)(R)(t) (I'm sure this comes into it somewhere, my teacher has brought it up.



    3. The way that my partner and I have carried out the experiment is:

    We would measure 50ml of water and pour it into a polystyrene cup. We would then use a digital thermometer to get a reading of the temperature of the water as a control. This varied each time we got new water and measured it, probably due to weather, humidity etc. We would connect a battery to a rheostat (variable resistor), then to an ammeter, then to a wire coil, which would be submerged in the water in the polystyrene cup, then back to the other battery terminal. So, we have been waiting 8 minutes for the water to heat up, each time with a different current, then measuring the temperature of the water and the increase from the control. How would this be relavent to a measurement in joules (What formula would I use to convert my readings in Celcius to Joules?)? I don't get it at all.

    Here are our results (A little weird, but we can... edit them, I know they're supposed to be directly related).

    table.jpg

    Thanks for any help, I hope I've been clear enough.

    Tom.
     
  2. jcsd
  3. Mar 30, 2009 #2

    rock.freak667

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    Re: Measure the relation between the current of a circuit and the heating effect prod

    use Q=mc(dT)

    Where is the mass of water
    c is the specific heat capacity of water
    dT is th temperature difference.
     
  4. Mar 30, 2009 #3
    Re: Measure the relation between the current of a circuit and the heating effect prod

    Thanks. To see if I've got it right:

    Q (heat in joules) = m (mass of water, 50ml/cc) x c (heat capacity of water, 4.186j/cm2) x dT (Difference from control, 0.03'C)
    = 6.279J

    Sorry if I got that completely wrong, I've never done anything like that before.
     
    Last edited: Mar 30, 2009
  5. Mar 30, 2009 #4

    rock.freak667

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    Re: Measure the relation between the current of a circuit and the heating effect prod

    yep, that would be the correct way to calculate it.
     
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