Themes > Science > Physics > Electromagnetism > Magnetostatics > Lorentz Force Law > Magnetohydrodynamics and the Lorentz Force Law > The Boat and Static Display
  • Firstly, you need to see how many batteries you need to carry on the boat. By experimentation and calculation it was found that the force produced by a current of 3A, supplied by a 9 volt battery, would do nicely. Is 9 volts enough to produce this current in a saturated salt water solution?
  • Use R = d/(A) where d is the distance the current travels
    •

    A is the cross sectional area of the material in which the current is traveling

    is the conductivity of the material

    In this case the material is a saturated salt water solution and:

  • d = 0.04 m is the distance between the electrodes
  • A = 0.0008 m2 is the area of an electrode = 22.6 (m)-1 for saturated salt water at 20 deg. Celsius
    •
  • Carrying the calculation through to get R = 2.21 . Now use Ohms Law: V = IR where I = 3A (short-circuit current of a 9 volt battery) V = 6.64 volts So a 9 volt battery should do the job.
    • If the water is not saturated, which was the case with my project, you might want to put some more batteries in series. (I had 3 in series; on the heave side)
    •

    The Motor

    The Static Display
    The Boat was made out of a large piece of plastic Styrofoam and looked a bit like a barge.

    The motor was attached to the bottom by the copper rods (see above). The batteries and switching mechanism (to switch the polarity of the electrodes) were contained in a waterproof Tupperware container mounted on top of the barge.
    (Sorry, no picture due to technical difficulties. You're just going to have to imagine it.)


    Information provided by: http://www.physics.ubc.ca