Wheatstone Bridge:Wheatstone Bridge is a type of electrical circuit used to measure unknown resistance values. It was invented by Samuel Hunter Christie in 1833 and later improved by Charles Wheatstone in 1843. The Wheatstone bridge consists of four resistors arranged in a bridge configuration, as shown in the diagram below.

R2
|
Vin — R1 — R3 — R4 — Vo
|
Rx

Wheatstone Bridge operates on the principle of balancing the potential difference across two arms of the bridge. When the bridge is balanced, the voltage difference between the points “Vin” and “Vo” is zero. By measuring the input voltage and the resistance values of R1, R2, R3, and R4, the unknown resistance value “Rx” can be calculated.

A Wheatstone bridge circuit consists of four arms, of which two arms consist of known resistances while the other two arms consist of an unknown resistance and a variable resistance. The circuit also consists of a galvanometer and an electromotive force source. The emf source is attached between points a and b while the galvanometer is connected between points c and d. The current that flows through the galvanometer depends on its potential difference.

Formula of Wheatstone Bridge

Following is the formula used for the Wheatstone bridge:

R = PS/Q

Where,

• R is the unknown resistance
• S is the standard arm of the bridge
• P and Q is the ratio of the arm of the bridge

Applications of Wheatstone Bridge

It is a commonly used electrical circuit that is used to measure an unknown electrical resistance. Some of the key applications of the Wheatstone bridge include:

• Measurement of resistance: It is commonly used to measure resistance, especially in precision applications where accuracy is important.
• Strain measurement: It is often used in strain gauges, which measure changes in resistance caused by physical strain on a material. This allows for the measurement of force, pressure, weight, and acceleration.
• Impedance measurement: It can be used to measure impedance, which is the opposition to the flow of alternating current in a circuit. This can be useful in applications such as audio and radio frequency electronics.
• Bridge balancing: It is often used to balance an electrical circuit, ensuring that the current flowing through the circuit is equal on both sides.

• Temperature measurement: By using temperature-sensitive resistors, such as thermistors, the Wheatstone bridge can be used to measure temperature.

Limitations of Wheatstone Bridge

The Wheatstone bridge has several limitations that should be considered when deciding whether it is the best choice for a particular application. Some of the key limitations include:

• Sensitivity: It is sensitive to small changes in resistance, but it may not be accurate enough for applications where extremely high precision is required.
• Power source: It requires a stable, low-noise power source to provide accurate results. If the power source is not stable, it can introduce errors into the measurement.
• Drift: Over time, the resistance of the components in the Wheatstone bridge may change due to temperature changes, aging, or other factors, leading to drift in the measurement.
• Calibration: It must be calibrated in order to provide accurate results. This calibration process can be time-consuming and must be repeated periodically to maintain accuracy.
• Range: It has a limited measurement range, and is not well-suited for measuring large resistances.
• Load resistance: It is sensitive to changes in load resistance, which can introduce errors into the measurement.

• Complexity: It can be a relatively complex circuit, which can make it difficult to design and construct, especially for inexperienced engineers.

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By Team Learning Mantras