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
+−15 VR1​ = 40 ΩR2​ = 300 ΩR3​ = 150 ΩR4​ = 250 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 15 V.

Vs = 15 VR1 = 40 ΩR2 = 300 ΩR3 = 150 ΩR4 = 250 Ω
Vab = V
2.Easy
+−6 VR1​ = 200 ΩR2​ = 250 ΩR3​ = ?R4​ = 250 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 200 Ω, R₂ = 250 Ω and R₄ = 250 Ω. Find the setting R3.

R1 = 200 ΩR2 = 250 ΩR4 = 250 Ω
R3 = Ω
3.Medium
+−9 V400 Ω400 Ω + ΔR400 Ω400 Ωab+−Vab​ = ?

A bridge has four 400 Ω arms and Vs = 9 V. The sensor R₂ increases by ΔR = 60 Ω. Find the exact output Vab in mV.

Vs = 9 VR = 400 ΩΔR = 60 Ω
Vab = mV
4.Medium
+−5 VR1​ = 10 ΩR2​ = 150 ΩR3​ = 150 ΩR4​ = 20 ΩabGRg​ = 200 Ω

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (Vs = 5 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 5 VR1 = 10 ΩR2 = 150 ΩR3 = 150 ΩR4 = 20 ΩRg = 200 Ω
Ig = µA
5.Hard
+−3 V120 Ω − ΔR120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 3 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.1 and the strain is 600 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2.1ε = 600 µε
Vo = mV
6.Hard
+−2.5 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−0.75 mV

A strain gauge (GF = 2) on a member with E = 70 GPa forms a quarter bridge excited with 2.5 V. The output reads 0.75 mV. Find the axial stress σ in MPa.

Vs = 2.5 VGF = 2Vo = 0.75 mVE = 70 GPa
σ = MPa

Answer key

  1. 1. Vab = 3.86 V
  2. 2. R3 = 200 Ω
  3. 3. Vab = 314 mV
  4. 4. Ig = 18057 µA
  5. 5. Vo = 1.89 mV
  6. 6. σ = 42 MPa

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