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​ = 40 ΩR3​ = 150 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 300 Ω, R₂ = 40 Ω and R₃ = 150 Ω. Find the unknown resistor R4.

R1 = 300 ΩR2 = 40 ΩR3 = 150 Ω
R4 = Ω
2.Easy
+−3 VR1​ = 400 ΩR2​ = 250 ΩR3​ = 60 ΩR4​ = 1000 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 3 V.

Vs = 3 VR1 = 400 ΩR2 = 250 ΩR3 = 60 ΩR4 = 1000 Ω
Vab = V
3.Medium
+−6 V200 Ω200 Ω200 Ω200 Ωab+−

A 200 Ω strain gauge is one arm (R₂) of a bridge with four equal 200 Ω arms and an excitation of 6 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 6 VR = 200 Ω
Pg = mW
4.Medium
+−2 V470 Ω470 Ω + ΔR470 Ω470 Ωab+−9.9 mV

A bridge with four 470 Ω arms is supplied with 2 V. When the sensor R₂ changes, the output reads Vab = 9.9 mV. Find the exact change ΔR of R₂.

Vs = 2 VR = 470 ΩVab = 9.9 mV
ΔR = Ω
5.Hard
+−10 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−3.18 mV

A strain gauge (GF = 2.12) on a member with E = 110 GPa forms a quarter bridge excited with 10 V. The output reads 3.18 mV. Find the axial stress σ in MPa.

Vs = 10 VGF = 2.12Vo = 3.18 mVE = 110 GPa
σ = MPa
6.Hard
+−3 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−0.636 mV

A quarter bridge with one active gauge (GF = 2.12) is excited with 3 V. Under load the output reads 0.636 mV. Find the strain ε in µε.

Vs = 3 VGF = 2.12Vo = 0.636 mV
ε = µε

Answer key

  1. 1. R4 = 20 Ω
  2. 2. Vab = −1.676 V
  3. 3. Pg = 45 mW
  4. 4. ΔR = 9.399 Ω
  5. 5. σ = 66 MPa
  6. 6. ε = 400 µε

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