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
+−5 VR1​ = 250 ΩR2​ = 600 ΩR3​ = 120 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 250 Ω, R₂ = 600 Ω and R₃ = 120 Ω. Find the unknown resistor R4.

R1 = 250 ΩR2 = 600 ΩR3 = 120 Ω
R4 = Ω
2.Easy
+−9 VR1​ = 800 ΩR2​ = 40 ΩR3​ = 150 ΩR4​ = 80 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 9 V.

Vs = 9 VR1 = 800 ΩR2 = 40 ΩR3 = 150 ΩR4 = 80 Ω
Vab = V
3.Medium
+−12 V300 Ω300 Ω + ΔR300 Ω300 Ωab+−339.6 mV

A bridge with four 300 Ω arms is supplied with 12 V. When the sensor R₂ changes, the output reads Vab = 339.6 mV. Find the exact change ΔR of R₂.

Vs = 12 VR = 300 ΩVab = 339.6 mV
ΔR = Ω
4.Medium
+−12 V400 Ω400 Ω + ΔR400 Ω400 Ωab+−Vab​ = ?

A bridge has four 400 Ω arms and Vs = 12 V. The sensor R₂ increases by ΔR = 20 Ω. Find the exact output Vab in mV.

Vs = 12 VR = 400 ΩΔR = 20 Ω
Vab = mV
5.Hard
+−V120 Ω120 Ω + ΔR120 Ω120 Ωab+−

A 120 Ω strain gauge with gauge factor 2.12 is bonded to a steel bar. Under load its resistance rises by 0.3053 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.12ΔR = 0.3053 Ω
ε = µε
6.Hard
+−3 V350 Ω − ΔR350 Ω + ΔR350 Ω + ΔR350 Ω − ΔRab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 3 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.12 and the strain is 1200 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2.12ε = 1200 µε
Vo = mV

Answer key

  1. 1. R4 = 288 Ω
  2. 2. Vab = −2.702 V
  3. 3. ΔR = 36 Ω
  4. 4. Vab = 146.3 mV
  5. 5. ε = 1200 µε
  6. 6. Vo = 7.632 mV

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