PURPOSE: To find an unknown EMF using a voltage divider.

DESCRIPTION: A battery of voltage V is connected across a resistive wire of length L. A second, unknown lesser voltage battery is connected through a meter to the slide tap of the potentiometer. Find the distance L₁ along the wire where the clip lead draws no current. The unknown voltage V_u is then:

V_u=V L₁/L

External batteries can be used to provide a different battery configuration if desired.

SUGGESTIONS:

REFERENCES: (PIRA 5F20.30)

EQUIPMENT: Slide wire potentiometer, external batteries (if needed), lecture galvanometer.

SETUP TIME: 5 min.