COLLEGE OF ENGINEERING AND SCIENCE LABORATORY EXPERIMENT The Potentiometer Name:_________________________ ID:____________________________ Date:___________________________ Experiment-ThePotentiometer.doc Page 2 LABORATORY EXPERIMENT The Potentiometer Circuit Introduction One of the original purposes of the potentiometer was to measure an unknown voltage using a known voltage as a reference. The potentiometer comprises a series of precision resistors which can be placed in series with a precision slide-wire resistor to create a known resistance. The instrument is connected to known and unknown voltages and the resistors are adjusted until the voltages are in balance. It is used in conjunction with a galvanometer which indicates when zero current flows and that the variable resistance is correctly adjusted. One advantage of using a potentiometer circuit to determine the value of an unknown voltage source is that, when the potentiometer circuit is balanced, no current flows through the circuit which avoids inaccurate measurements due to internal resistances. More common applications of the potentiometer can be seen in the volume control on a radio or stereo, although this has been superseded by digital controls which click up or down. Today’s experiment expands on the techniques introduced in the laboratory, Measurement of Resistance, again using concepts given by Ohm’s and Kirchhoff’s laws. Aims Today’s laboratory aims to teach students how to connect a variety of electrical circuits in order to undertake reliable electrical measurements. This exercise is primarily a practical one which will: (a) provide experience in wiring up a potentiometer circuit, (b) use that circuit to measure unknown emfs, (c) use a potentiometer to calibrate an ammeter Reference Serway, R. A. and Beichner, R.J. (2000), Physics for Scientists and Engineers with Modern Physics, 5th ed., Saunders College Publishing, Ch. 28. Preliminary Questions The Concept of a Potentiometer 1. State the difference between the terms, electromotive force (emf) and terminal voltage, when referring to a battery? Include a reason for the numerical difference between the two in your answer and an equation relating the emf, , to the terminal voltage, V. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ .