Wheatstone bridge & strain gauges worksheet with answers

Free printable Wheatstone bridge & strain gauges worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 12 V.

V_s = 12 VR₁ = 40 ΩR₂ = 50 ΩR₃ = 300 ΩR₄ = 150 Ω

V_ab = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 40 Ω, R₂ = 50 Ω and R₃ = 600 Ω. Find the unknown resistor R₄.

R₁ = 40 ΩR₂ = 50 ΩR₃ = 600 Ω

R₄ = Ω

3.Medium

A bridge with four 1000 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads V_ab = 7.46 mV. Find the exact change ΔR of R₂.

V_s = 3 VR = 1000 ΩV_ab = 7.46 mV

ΔR = Ω

4.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 6 VR₁ = 800 ΩR₂ = 800 ΩR₃ = 400 ΩR₄ = 600 Ω

R_th = Ω

5.Hard

A 1000 Ω strain gauge with gauge factor 2.12 is bonded to a steel bar. Under load its resistance rises by 0.53 Ω. Find the strain ε in microstrain (µε).

R = 1000 ΩGF = 2.12ΔR = 0.53 Ω

ε = µε

6.Hard

A bridge with 1000 Ω arms is excited with 5 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2.05ε = 1000 µε

V_o = mV

Answer key

1. V_ab = 2.667 V
2. R₄ = 750 Ω
3. ΔR = 9.996 Ω
4. R_th = 640 Ω
5. ε = 250 µε
6. V_o = 2.563 mV

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