Making and Using A Microbalance

A microbalance is a highly sensitive instrument used to measure very small masses that cannot be measured using ordinary weighing scales. In this activity, we constructed a simple microbalance using easily available materials such as a straw, a clamp stand, and a graph sheet to understand the measurement of extremely light objects. The working of this microbalance is based on the principle of a lever. The straw acts as a lever, and the point where it is fixed using a clamp or support acts as the fulcrum. One end of the straw is free to move, and when a small mass is placed on this end, it produces a turning effect, causing the straw to tilt downward. The amount of tilt depends on the mass attached. To measure this tilt accurately, a graph sheet was placed vertically behind the free end of the straw. This helped in observing and recording the deflection (displacement) of the straw with respect to a reference point. The graph sheet provided a scale to quantify even very small movements. Before measuring unknown objects, the microbalance was first standardized (calibrated) using small, known quantities of paper bits of 1 cm square . These paper bits acted as reference masses. Different numbers of paper bits were added to the free end of the straw, and the corresponding deflection was recorded each time. This process helped in establishing a relationship between mass and deflection, effectively creating a calibration scale. After standardization, the actual objects such as a small plant leaf and a small hair strand were placed on the same end of the straw. The deflection caused by these objects was carefully observed on the graph sheet. By comparing this deflection with the previously recorded values from the paper bits, the approximate mass of the leaf and hair strand was determined. This method does not involve direct comparison with another mass at the same time but instead relies on prior calibration and the relationship between mass and deflection.