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Jumping Wire / Parallel Currents

 

High current from the jump starter makes the wires jump together or apart, depending on how the circuit is wired.  Connections are set up so that the clamps can be attached to the bottoms of the two lamp wires for antiparallel currents (series) or so that one clamp can be connected to the black-coated third wire and the other to the two lamp wires together for parallel currents.

Make sure not to leave the current on for very long, as the wires will get hot enough to melt the insulation.  The instructions for the jump starter say to leave it plugged in when it’s not in use.

Location: L01, section B2

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Parallel Currents

Parallel Currents demo picture

force on parallel wires

  • Demonstrate force between parallel currents.
  • Using two power supplies, send current through both stationary and balancing wires.
  • Angle of mirror connected to pivot will change as wires are pulled together or pushed apart due to Lorentz force. A laser beam, deflected by mirror, can be used to show the otherwise imperceptible change of mirror angle.
  • To determine the strength of the Lorentz force: mark the laser position on a distant wall both with and without current- using current that produces attraction, not repulsion. Then, with current off, place small pieces of folded up tin foil on top of movable wire (using platform on wire) until deflection of laser matches that produced by Lorentz force. Weigh tin foil pieces with sensitive digital scale to determine gravitational force.
  • Compare gravitational force to Lorentz force.
  • Distance between wires, and wire length, can be measured using ruler. Current can be measured using Ammeter.
  • Current balance located in L01, section B3.
  • Power supply, laser, digital scale, ammeter, and tin foil in L35.