Potentiometer Lab Report

OBJECTIVE

The objective of this experiment is to learn about the operation of potentiometer. Next, the objective is to build a Wheatstone bridge to measure unknown resistances.

INTRODUCTION

A Wheatstone bridge is an electrical circuit used to measure the resistance of an unknown resistor. It measures the resistance by balancing two legs of a bridge circuit, one leg includes the unknown component. The Wheatstone bridge permits a precise measurement which mirrors the function of potentiometer. However, in a potentiometer circuits, the meter used is sensitive galvanometer. The Wheatstone bridge circuit can be used in two ways which is balanced bridge and unbalanced bridge. A schematic of a Wheatstone bridge is shown below:

Figure 1:

The potentiometer value was varied by x such that 1k + x was the new value of Rx.

8. The output voltage across a-b, Vab was measured.

9. The potentiometer values with fixed increments of x were varied while steps 6 – 7 were being repeated.

10. Table 1 was tabulated.

11. Findings were discussed and all relevant calculations in the report were showed.

Balanced condition

1. Three fixed resistors, R1, R2, R3 and one potentiometer Rx were selected. The resistances of the fixed resistors and the potentiometer were measured by using a multimeter. These values were noted down in Table 2 as the measured values.

2. The power supply was set to 5V.

3. The circuit was connected as shown in Figure 1.

4. The expected value of Rx was calculated when the bridge is in a balance state, Vab = 0.

5. The potentiometer, Rx, was tuned until Vab was zero while measuring the output voltage across a-b, Vab.

6. Three different values of R1, R2, R3 were selected. These values were noted down in Table 2.

7. Steps 3- 6 were repeated. Table 2 was populated.

8. Findings were discussed and all relevant calculations in report were showed.

PRECAUTIONS:
1. Always turn the test equipment off when it is not in