Wheatstone Bridge

Definition

A Wheatstone bridge is an electrical circuit used to measure unknown resistances by balancing two legs of a bridge circuit. This setup helps in determining the precise value of an unknown resistor by comparing it with known resistors, which is essential in applications like sensor calibration and resistance measurement in circuits.

5 Must Know Facts For Your Next Test

1. The Wheatstone bridge consists of four resistors arranged in a diamond shape, with a voltage source connected across one diagonal and a galvanometer across the other diagonal.
2. When the bridge is balanced, the ratio of the two known resistors is equal to the ratio of the two unknown resistors, allowing for precise calculations of resistance.
3. This circuit is particularly useful for measuring small changes in resistance, making it ideal for applications like strain gauges and temperature sensors.
4. The Wheatstone bridge can be modified into a bridge circuit for AC signals, which can help analyze frequency response and impedance.
5. Calibration of instruments can be performed using a Wheatstone bridge by comparing standard resistors against unknown resistances to ensure accuracy.

Review Questions

• How does a Wheatstone bridge allow for the measurement of unknown resistances, and what conditions must be met for it to function properly?
  • A Wheatstone bridge measures unknown resistances by balancing two legs of the circuit with known resistances. For it to function properly, the ratio of the known resistances must equal the ratio of the unknown resistance to another known resistor when balanced. This results in zero voltage across the galvanometer, indicating that the bridge is in equilibrium, allowing for accurate calculation of the unknown resistance.
• Discuss how the Wheatstone bridge can be adapted for use with AC signals and its advantages in analyzing circuits.
  • The Wheatstone bridge can be adapted for AC signals by incorporating components like capacitors or inductors into its design. This modification allows engineers to analyze not just resistance but also reactance and impedance in circuits at different frequencies. The advantage of this approach is that it provides a comprehensive understanding of circuit behavior under alternating current conditions, which is crucial for designing filters and tuning circuits.
• Evaluate the impact of using a Wheatstone bridge on precision measurement in electrical engineering applications.
  • Using a Wheatstone bridge significantly enhances precision measurement in electrical engineering applications. Its ability to balance resistances means that it can detect very small changes in resistance with high accuracy. This is particularly important in applications such as sensor calibration where even minor variations can affect performance. By providing precise resistance values, the Wheatstone bridge contributes to better overall system performance and reliability.

Related terms

Resistance:

The opposition to the flow of electric current, measured in ohms, and is a fundamental property of electrical components.

Ohm's Law:

A principle that states the current through a conductor between two points is directly proportional to the voltage across the two points, expressed as V = IR.

Potentiometer: An instrument used to measure the voltage in a circuit by balancing it against a known voltage, often used in conjunction with a Wheatstone bridge.