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
+−12 VR1​ = 50 ΩR2​ = 1000 ΩR3​ = 120 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 50 Ω, R₂ = 1000 Ω and R₃ = 120 Ω. Find the unknown resistor R4.

R1 = 50 ΩR2 = 1000 ΩR3 = 120 Ω
R4 = Ω
2.Easy
+−5 VR1​ = 500 ΩR2​ = 120 ΩR3​ = ?R4​ = 150 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 500 Ω, R₂ = 120 Ω and R₄ = 150 Ω. Find the setting R3.

R1 = 500 ΩR2 = 120 ΩR4 = 150 Ω
R3 = Ω
3.Medium
+−2 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−56.6 mV

A bridge with four 120 Ω arms is supplied with 2 V. When the sensor R₂ changes, the output reads Vab = 56.6 mV. Find the exact change ΔR of R₂.

Vs = 2 VR = 120 ΩVab = 56.6 mV
ΔR = Ω
4.Medium
+−2 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−9.9 mV

A bridge with four 350 Ω arms is supplied with 2 V. When the sensor R₂ changes, the output reads Vab = 9.9 mV. Find the exact change ΔR of R₂.

Vs = 2 VR = 350 ΩVab = 9.9 mV
ΔR = Ω
5.Hard
+−5 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 5 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 750 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2.05ε = 750 µε
Vo = mV
6.Hard
+−3 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−1.5 mV

A strain gauge (GF = 2) on a member with E = 110 GPa forms a quarter bridge excited with 3 V. The output reads 1.5 mV. Find the axial stress σ in MPa.

Vs = 3 VGF = 2Vo = 1.5 mVE = 110 GPa
σ = MPa

Answer key

  1. 1. R4 = 2400 Ω
  2. 2. R3 = 625 Ω
  3. 3. ΔR = 14.4 Ω
  4. 4. ΔR = 6.999 Ω
  5. 5. Vo = 1.922 mV
  6. 6. σ = 110 MPa

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