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
+−5 VR1​ = 40 ΩR2​ = 20 ΩR3​ = 150 ΩR4​ = 20 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 5 V.

Vs = 5 VR1 = 40 ΩR2 = 20 ΩR3 = 150 ΩR4 = 20 Ω
Vab = V
2.Easy
+−12 VR1​ = 1000 ΩR2​ = 400 ΩR3​ = 150 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 1000 Ω, R₂ = 400 Ω and R₃ = 150 Ω. Find the unknown resistor R4.

R1 = 1000 ΩR2 = 400 ΩR3 = 150 Ω
R4 = Ω
3.Medium
+−6 V100 Ω100 Ω + ΔR100 Ω100 Ωab+−Vab​ = ?

A bridge has four 100 Ω arms and Vs = 6 V. The sensor R₂ increases by ΔR = 20 Ω. Find the exact output Vab in mV.

Vs = 6 VR = 100 ΩΔR = 20 Ω
Vab = mV
4.Medium
+−12 V150 Ω150 Ω + ΔR150 Ω150 Ωab+−59.41 mV

A bridge with four 150 Ω arms is supplied with 12 V. When the sensor R₂ changes, the output reads Vab = 59.41 mV. Find the exact change ΔR of R₂.

Vs = 12 VR = 150 ΩVab = 59.41 mV
ΔR = Ω
5.Hard
+−10 V350 Ω − ΔR350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 10 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2 and the strain is 1200 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2ε = 1200 µε
Vo = mV
6.Hard
+−V120 Ω120 Ω + ΔR120 Ω120 Ωab+−

A 120 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.144 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2ΔR = 0.144 Ω
ε = µε

Answer key

  1. 1. Vab = 1.078 V
  2. 2. R4 = 60 Ω
  3. 3. Vab = 272.7 mV
  4. 4. ΔR = 3 Ω
  5. 5. Vo = 12 mV
  6. 6. ε = 600 µε

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