# Wheatstone Bridge Calculator

This *Wheatstone bridge* calculator will compute the value of the unknown resistor R4, providing you enter the values of R1, R2, and the value of variable resistor VR3 at null point.

In these types of experiments, we usually make the ratio of R1 and R2 a factor of 10. We place the resistor of unknown value in position R4, and then adjust the variable resistor VR3 until the voltmeter reads zero volts, which boffins call a
*null point*. At the null point, boffins like to say that the bridge is *balanced*. When the bridge is balanced, the following equation applies:

**R4 = VR3 × (R2/R1)**

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