5H40.10 "Current Balance"

PURPOSE: To demonstrate the forces on current in wires

DESCRIPTION: A finely pivoted frame holds a current-carrying bar above another current-carrying bar. The bars move toward each other when the currents are in the same direction, and repel when the currents are switched to flow in opposite directions.

SETUP TIME: Medium

COMPONENT LIST:

    


  1.  Frame with current-carrying bars			EM Shelves


  2.  Current source

SUGGESTIONS: See Vincent's 2122 Demonstration Booklet for further instructions.

REFERENCES: 2122 4.6; PIRA 5H40.10

OTHER NOTES: This is the basis of the absolute definition of the ampere. (One ampere is that unvarying current which, if present in each of two parallel conductors of infinite length and one meter apart in empty space, causes each conductor to experience a force of exactly 2 x 10-7 newton per meter of length. This definition was adopted in 1940.)