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
+−6 VR1​ = 300 ΩR2​ = 20 ΩR3​ = ?R4​ = 100 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 300 Ω, R₂ = 20 Ω and R₄ = 100 Ω. Find the setting R3.

R1 = 300 ΩR2 = 20 ΩR4 = 100 Ω
R3 = Ω
2.Easy
+−12 VR1​ = 300 ΩR2​ = 100 ΩR3​ = 600 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 300 Ω, R₂ = 100 Ω and R₃ = 600 Ω. Find the unknown resistor R4.

R1 = 300 ΩR2 = 100 ΩR3 = 600 Ω
R4 = Ω
3.Medium
+−10 VR1​ = 1000 ΩR2​ = 400 ΩR3​ = 50 ΩR4​ = 50 Ωab+−Rth​ = ?

Find the Thévenin resistance Rth of the bridge shown, seen from the output terminals a and b.

Vs = 10 VR1 = 1000 ΩR2 = 400 ΩR3 = 50 ΩR4 = 50 Ω
Rth = Ω
4.Medium
+−3 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vab​ = ?

A bridge has four 350 Ω arms and Vs = 3 V. The sensor R₂ increases by ΔR = 87.5 Ω. Find the exact output Vab in mV.

Vs = 3 VR = 350 ΩΔR = 87.5 Ω
Vab = mV
5.Hard
+−10 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−2.12 mV

A strain gauge (GF = 2.12) on a member with E = 210 GPa forms a quarter bridge excited with 10 V. The output reads 2.12 mV. Find the axial stress σ in MPa.

Vs = 10 VGF = 2.12Vo = 2.12 mVE = 210 GPa
σ = MPa
6.Hard
+−5 V1000 Ω − ΔR1000 Ω + ΔR1000 Ω1000 Ωab+−Vo​ = ?

A bridge with 1000 Ω arms is excited with 5 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 1000 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2.1ε = 1000 µε
Vo = mV

Answer key

  1. 1. R3 = 1500 Ω
  2. 2. R4 = 200 Ω
  3. 3. Rth = 310.7 Ω
  4. 4. Vab = 166.7 mV
  5. 5. σ = 84 MPa
  6. 6. Vo = 5.25 mV

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