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๐ŸŽขprinciples of physics ii review

Ratio of resistances

Written by the Fiveable Content Team โ€ข Last updated September 2025
Written by the Fiveable Content Team โ€ข Last updated September 2025

Definition

The ratio of resistances is a comparison of two or more resistors in an electrical circuit, often expressed as a fraction or a decimal. This concept is particularly important in circuits that use configurations like the Wheatstone bridge, where the relationship between the resistances determines the balance and allows for precise measurements of unknown resistances.

5 Must Know Facts For Your Next Test

  1. In a Wheatstone bridge, the ratio of resistances helps determine if the bridge is balanced, which occurs when the voltage across the bridge's output is zero.
  2. The formula for balance in a Wheatstone bridge states that if R1/R2 = R3/Rx (where Rx is the unknown resistance), the bridge is balanced.
  3. The ratio of resistances can be used to calculate unknown values in various applications, including sensor calibration and material testing.
  4. When resistances are in series, their total resistance is simply the sum of their individual resistances, affecting the overall ratio when analyzed in circuits.
  5. Understanding how to manipulate and apply the ratio of resistances is crucial for troubleshooting circuits and designing effective electronic devices.

Review Questions

  • How does the ratio of resistances affect the functionality of a Wheatstone bridge?
    • The ratio of resistances is essential for determining whether a Wheatstone bridge is balanced. When R1/R2 equals R3/Rx, where Rx is the unknown resistor, the output voltage across the bridge becomes zero. This balance allows for accurate measurement of Rx and demonstrates how critical these ratios are in ensuring precise electrical measurements.
  • Evaluate how changing one resistor in a Wheatstone bridge impacts its overall function regarding resistance ratios.
    • Changing one resistor in a Wheatstone bridge alters the resistance ratios and can lead to an imbalance. For example, if R1 increases while R2 remains constant, then the ratio R1/R2 increases. This shift can cause the output voltage across the bridge to no longer equal zero, indicating that recalibration or adjustment may be necessary to regain balance and accurately measure any unknown resistance.
  • Discuss how understanding the ratio of resistances can enhance practical applications in engineering and technology.
    • Understanding the ratio of resistances allows engineers and technicians to design more efficient circuits and accurately measure components within those circuits. For instance, in sensor technology, knowing how resistance ratios change with environmental factors enables better calibration and responsiveness. This knowledge not only improves performance but also aids in diagnosing faults within electronic systems, ultimately leading to more reliable technological solutions.