What is the balance condition of a Wheatstone bridge?

A Wheatstone bridge is balanced when the ratio R1/R2 equals R3/Rx, or equivalently R1 x Rx = R2 x R3. At balance, the voltage across the galvanometer is zero and no current flows through it. The unknown resistance is then Rx = R2 x R3 / R1.

How do you calculate the unknown resistance using a Wheatstone bridge?

To find the unknown resistance Rx, adjust the known resistors R1, R2, and R3 until the galvanometer reads zero (null condition). Then apply the formula Rx = R2 x R3 / R1. This null-detection method is very accurate because it does not depend on the galvanometer's calibration.

What is the sensitivity of a Wheatstone bridge?

Bridge sensitivity is the change in galvanometer current or bridge voltage per unit change in resistance. Maximum sensitivity occurs when all four arms have equal resistance. Sensitivity also depends on supply voltage and galvanometer internal resistance. Higher sensitivity means the bridge can detect smaller resistance changes.

Wheatstone Bridge

Balanced & Unbalanced Circuit Analysis • Galvanometer Deflection • Unknown Resistance — Simulate • Explore • Practice • Quiz

Mode

R1 (Ω) 1000 Ω

R2 (Ω) 1000 Ω

R3 (Ω) 1000 Ω

Rx (Ω) 1000 Ω

V Supply (V) 12.0 V

Show Galvanometer Deflection Auto-Balance Mode

Presets

Rx (Calculated)

1000.0 Ω

Bridge Voltage

0.000 V

Galv. Current

0.000 mA

Balance Status

Balanced

Sensitivity

0.000 mA/Ω

Understanding the Wheatstone Bridge — Free Interactive Circuit Simulator

The Wheatstone bridge is one of the most important measurement circuits in electrical engineering. Invented by Samuel Hunter Christie in 1833 and later popularized by Sir Charles Wheatstone, it provides an extremely accurate method for measuring unknown resistances. The bridge consists of four resistors arranged in a diamond (or square) configuration with a voltage source across one diagonal and a galvanometer across the other. When the bridge is balanced — meaning R1/R2 = R3/Rx — no current flows through the galvanometer and the unknown resistance can be calculated as Rx = R2 × R3 / R1. This null-detection method is independent of the galvanometer’s sensitivity or calibration, making it far more accurate than direct measurement methods.

How the Wheatstone Bridge Works

The bridge circuit divides the supply voltage into two voltage dividers connected in parallel. The top divider consists of R1 and R3, while the bottom divider consists of R2 and Rx. The galvanometer measures the potential difference between the midpoints of these two dividers. When the voltage at both midpoints is equal, the bridge is balanced and the galvanometer reads zero. The bridge voltage is calculated as V_bridge = V_s × (R3/(R1+R3) − Rx/(R2+Rx)). Any imbalance causes current to flow through the galvanometer, with the direction indicating whether Rx is too high or too low.

Applications of the Wheatstone Bridge

Wheatstone bridges are used extensively in strain gauge measurements, where tiny resistance changes (as small as 0.01%) must be detected accurately. Temperature sensors, pressure transducers, and load cells all use bridge configurations. The Kelvin double bridge extends the concept to measure very low resistances (below 1 ohm) by eliminating lead and contact resistance errors. In laboratory settings, the meter bridge (slide-wire bridge) and post office box are practical implementations of the Wheatstone bridge principle.

Who Uses This Simulator?

This simulator is designed for electrical engineering students, physics students studying DC circuits and measurement techniques, instrumentation engineers learning about bridge circuits, and TVET trainees working with resistance measurement. It provides hands-on visual understanding of bridge balance, galvanometer deflection, and sensitivity analysis without requiring laboratory equipment.

Explore Related Simulators

If you found this Wheatstone Bridge simulator helpful, explore our Ohm’s Law simulator, RC Circuit simulator, RLC Circuit simulator, Transformer simulator, and Star-Delta Conversion simulator for more hands-on practice.