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
+−3 VR1​ = 20 ΩR2​ = 1000 ΩR3​ = ?R4​ = 150 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 20 Ω, R₂ = 1000 Ω and R₄ = 150 Ω. Find the setting R3.

R1 = 20 ΩR2 = 1000 ΩR4 = 150 Ω
R3 = Ω
2.Easy
+−12 VR1​ = 250 ΩR2​ = 1000 ΩR3​ = ?R4​ = 60 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 250 Ω, R₂ = 1000 Ω and R₄ = 60 Ω. Find the setting R3.

R1 = 250 ΩR2 = 1000 ΩR4 = 60 Ω
R3 = Ω
3.Medium
+−12 V150 Ω150 Ω + ΔR150 Ω150 Ωab+−Vab​ = ?

A bridge has four 150 Ω arms and Vs = 12 V. The sensor R₂ increases by ΔR = 1.5 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 12 VR = 150 ΩΔR = 1.5 Ω
Vab = mV
4.Medium
+−2 VR1​ = 800 ΩR2​ = 300 ΩR3​ = 80 ΩR4​ = 40 ΩabGRg​ = 100 Ω

A galvanometer with a resistance of 100 Ω is connected between a and b of the bridge shown (Vs = 2 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 2 VR1 = 800 ΩR2 = 300 ΩR3 = 80 ΩR4 = 40 ΩRg = 100 Ω
Ig = µA
5.Hard
+−10 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 10 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 = 10 VGF = 2ε = 1500 µε
Vo = mV
6.Hard
+−5 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−3.844 mV

A strain gauge (GF = 2.05) on a member with E = 70 GPa forms a quarter bridge excited with 5 V. The output reads 3.844 mV. Find the axial stress σ in MPa.

Vs = 5 VGF = 2.05Vo = 3.844 mVE = 70 GPa
σ = MPa

Answer key

  1. 1. R3 = 3 Ω
  2. 2. R3 = 15 Ω
  3. 3. Vab = 30 mV
  4. 4. Ig = −351.5 µA
  5. 5. Vo = 7.5 mV
  6. 6. σ = 105 MPa

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