Force on Current in Wires – 5H40.00

Current Coil, OHP – 5H40.20


  • Connect a piece of slinky to a one terminal of a power supply, about 10-20 volts.
  • Place the coil on OHP
  • Tough the other connection from the power supply to the coil momentarily. (Don’t attach it–just touch it). Watch the coil of wire quickly contract as current flows through it.

Location: Jacobs B122 – Shelf 280

Current Balance – 5H40.40

Current Balance 5H40.40

  • This demo is used to illustrate the magnetic fields around current carrying wires.
  • Connect the current balance apparatus to a rheostat and a power supply.
  • Adjust the balance so that it moves freely that the top wire is above but not resting on the bottom wire.
  • A laser can be shined to the mirror so that the laser reflection will show clearly on a screen.
  • Turn on the power supply and apply current gradually.
  • As more current is applied, the parallel wires will attract or repel each other depending on the direction of the current.

Location:Demo Room

Homopolar Motor – 5H40.53

Homopolar MotorII_5H40531 HomopoMotorC_5H4053

  • A spherical magnet hangs from a deck screw attracted to the negative terminal of a D cell battery (forming a low-friction bearing).
  • A wire is used to complete the circuit between the positive terminal of the battery and the magnet. This causes the magnet to spin.


  • Place a battery base on a magnet.
  • Place the wire loop on top of the battery and see the loop turn.

Location: Jacobs B122 – Shelf 276

Magnet Car – 5H40.54


  • Place two magnets with similar poles facing outward on opposite ends of a AA battery.
  • Place a sheet of thin aluminum foil on a flat non-magnetic surface
  • Place the battery assembly on the foil and watch as it rolls

Location: Jacobs B122 – Shelf 263

Magnet Train – 5H40.55


  • Place two magnets with similar poles facing outward on opposite ends of a AA battery.
  • Place the assembly into the copper coil
  • If it doesn’t move forward, turn the battery around

Location: Jacobs B122 – Shelf 263