In simple terms, half deflection in a galvanometer refers to the state where the galvanometer's needle deflects to exactly half of its maximum possible reading.
Understanding Half Deflection
Half deflection is a specific measurement point utilized within a particular experimental method known as the half deflection technique. This technique is employed in electrical measurements, primarily involving circuits with a sensitive galvanometer, a cell (voltage source), and resistances.
According to the provided reference:
- The half deflection technique is a way of analyzing a cell's internal resistance to aid in determining a high-value resistance.
- The deflection of half would be regarded as a value received only from the cell.
Therefore, within this context, achieving half deflection serves a specific purpose related to isolating or utilizing a measurement influenced solely by the cell's characteristics (like its voltage or internal resistance) for further calculations, particularly when dealing with larger external resistances.
Purpose of the Half Deflection Technique
The half deflection method is a practical approach used in laboratory settings. Its main objectives include:
- Determining the internal resistance of a cell: By observing the galvanometer deflection with and without an additional resistance in the circuit, and specifically noting the point where the deflection is halved, one can calculate the internal resistance of the voltage source (cell).
- Measuring unknown high resistances: Once the internal resistance of the cell and the characteristics of the galvanometer (resistance) are known, the half deflection principle can be extended to measure external resistances, especially those with high values, by setting up specific circuit configurations.
How it Works (Conceptual Basis)
While the detailed circuit analysis is beyond the scope of this basic definition, the core idea revolves around Ohm's Law and circuit analysis. When a galvanometer is connected to a cell, it shows a certain deflection proportional to the current flowing through it. By adding resistance in series or parallel and adjusting until the original deflection is precisely halved, a relationship between the galvanometer's resistance, the added resistance, and the cell's internal resistance is established. This allows for the calculation of the unknown values.
Essentially, achieving "half deflection" provides a controlled condition or a known ratio of currents (or voltages, depending on the circuit setup) within the circuit, which simplifies the equations needed to solve for unknown resistances.
