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​ = 20 ΩR2​ = 150 ΩR3​ = 20 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 20 Ω, R₂ = 150 Ω and R₃ = 20 Ω. Find the unknown resistor R4.

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

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 20 Ω, R₂ = 1000 Ω and R₄ = 250 Ω. Find the setting R3.

R1 = 20 ΩR2 = 1000 ΩR4 = 250 Ω
R3 = Ω
3.Medium
+−10 V150 Ω150 Ω + ΔR150 Ω150 Ωab+−Vab​ = ?

A bridge has four 150 Ω arms and Vs = 10 V. The sensor R₂ increases by ΔR = 15 Ω. Find the exact output Vab in mV.

Vs = 10 VR = 150 ΩΔR = 15 Ω
Vab = mV
4.Medium
+−6 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vab​ = ?

A bridge has four 350 Ω arms and Vs = 6 V. The sensor R₂ increases by ΔR = 70 Ω. Find the exact output Vab in mV.

Vs = 6 VR = 350 ΩΔR = 70 Ω
Vab = mV
5.Hard
+−5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−0.525 mV

A strain gauge (GF = 2.1) on a member with E = 210 GPa forms a quarter bridge excited with 5 V. The output reads 0.525 mV. Find the axial stress σ in MPa.

Vs = 5 VGF = 2.1Vo = 0.525 mVE = 210 GPa
σ = MPa
6.Hard
+−V350 Ω350 Ω + ΔR350 Ω350 Ωab+−

A 350 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 0.441 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2.1ΔR = 0.441 Ω
ε = µε

Answer key

  1. 1. R4 = 150 Ω
  2. 2. R3 = 5 Ω
  3. 3. Vab = 238.1 mV
  4. 4. Vab = 272.7 mV
  5. 5. σ = 42 MPa
  6. 6. ε = 600 µε

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