Wheatstone Bridge Calculator
Find the unknown resistance in a balanced Wheatstone bridge.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Enter the three known resistances R1, R2, and R3. The calculator computes R4 using the balance condition R4 = R3 x R2 / R1.
About Wheatstone Bridge
The Wheatstone bridge, invented by Samuel Hunter Christie and popularized by Sir Charles Wheatstone, is a circuit for precisely measuring electrical resistance. It consists of four resistors arranged in a diamond with a sensitive galvanometer across the midpoints. When the bridge is balanced, no current flows through the galvanometer, and the unknown resistance can be calculated from the three known values. Modern applications include strain gauges, load cells, and temperature sensors.
Frequently Asked Questions
What is a Wheatstone bridge?
A Wheatstone bridge is a circuit of four resistors in a diamond arrangement with a galvanometer across the middle. When balanced, the galvanometer reads zero and the unknown resistance can be calculated.
When is the bridge balanced?
The bridge is balanced when R1/R2 = R3/R4. At balance, no current flows through the galvanometer, and the unknown resistance R4 = R3 x R2 / R1.
Where are Wheatstone bridges used?
They are used for precision resistance measurement, strain gauges, temperature sensors (RTDs), and any application requiring accurate measurement of small resistance changes.