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
+−10 VR1​ = 10 ΩR2​ = 40 ΩR3​ = 150 ΩR4​ = 80 Ωab+−

The bridge shown is supplied with Vs = 10 V and its output is open. Find the current Is drawn from the supply, in mA.

Vs = 10 VR1 = 10 ΩR2 = 40 ΩR3 = 150 ΩR4 = 80 Ω
Is = mA
2.Easy
+−5 VR1​ = 120 ΩR2​ = 150 ΩR3​ = 400 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 120 Ω, R₂ = 150 Ω and R₃ = 400 Ω. Find the unknown resistor R4.

R1 = 120 ΩR2 = 150 ΩR3 = 400 Ω
R4 = Ω
3.Medium
+−6 V250 Ω250 Ω + ΔR250 Ω250 Ωab+−115.4 mV

A bridge with four 250 Ω arms is supplied with 6 V. When the sensor R₂ changes, the output reads Vab = 115.4 mV. Find the exact change ΔR of R₂.

Vs = 6 VR = 250 ΩVab = 115.4 mV
ΔR = Ω
4.Medium
+−3 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−36.59 mV

A bridge with four 120 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads Vab = 36.59 mV. Find the exact change ΔR of R₂.

Vs = 3 VR = 120 ΩVab = 36.59 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 and the strain is 1500 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2ε = 1500 µε
Vo = mV
6.Hard
+−5 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−0.663 mV

A strain gauge (GF = 2.12) on a member with E = 70 GPa forms a quarter bridge excited with 5 V. The output reads 0.663 mV. Find the axial stress σ in MPa.

Vs = 5 VGF = 2.12Vo = 0.663 mVE = 70 GPa
σ = MPa

Answer key

  1. 1. Is = 243.5 mA
  2. 2. R4 = 500 Ω
  3. 3. ΔR = 20 Ω
  4. 4. ΔR = 6.001 Ω
  5. 5. Vo = 3.75 mV
  6. 6. σ = 17.51 MPa

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