- Why is a Wheatstone bridge more accurate than a simple multimeter for measuring resistance?
- A Wheatstone bridge uses a null measurement method, where the galvanometer reads zero at balance. This means the measurement does not depend on the precision of the meter's calibration, only on the known resistor values and the balance condition. It minimizes errors from meter resistance and power supply fluctuations, allowing for highly precise measurements, often to fractions of an ohm.
- What happens if the galvanometer is replaced with a voltmeter in the simulator?
- A modern digital voltmeter has very high input impedance, drawing minimal current. It would display the potential difference (V_B − V_C) directly. While useful for observing the unbalanced bridge voltage, it would not show the true null condition as sharply as a sensitive galvanometer, as a tiny current might still flow. The fundamental balance condition, however, remains the same.
- Is the Wheatstone bridge only used for measuring resistors?
- No. While its primary function is precise resistance measurement, the principle is widely used in sensor applications. Sensors that change resistance with temperature, strain, or light (like strain gauges in load cells or thermistors) are often placed in one arm of a Wheatstone bridge. The bridge converts the small resistance change into a measurable voltage output, making it a fundamental circuit in instrumentation.
- What is a key limitation of the basic Wheatstone bridge model shown?
- The ideal model assumes perfectly known fixed resistors and zero wire resistance. In practice, contact resistances and lead wire resistances can introduce errors, especially when measuring very low resistances. For such cases, modified bridges like the Kelvin (Thomson) double bridge are used. The simulator also assumes a perfectly stable DC voltage source.