PURPOSE: To demonstrate visually the force between two parallel currents.

DESCRIPTION: This is a visualization of the force between two current-carrying wires. The discharge tube produces an electron beam moving from left to right, which can be seen on the fluorescent screen inside the tube. Activating an electric current along the top of the discharge tube (parallel to the electron beam) deflects the electron beam up or down. The current in the outside wire can be reversed to verify that the force is a vector.

Click on the picture above to see the displacement of the beam with the current ON.

SUGGESTIONS: See Question of the Week #68 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 5H30.15) See Demonstration K1-01: FORCE BETWEEN CURRENT-CARRYING WIRES.

EQUIPMENT: Cathode ray tube with 5 kV power supply, additional mounted parallel wire with 7.5 volt battery and key.

SETUP TIME: 5 min.