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​ = 100 ΩR2​ = 150 ΩR3​ = 500 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 100 Ω, R₂ = 150 Ω and R₃ = 500 Ω. Find the unknown resistor R4.

R1 = 100 ΩR2 = 150 ΩR3 = 500 Ω
R4 = Ω
2.Easy
+−12 VR1​ = 400 ΩR2​ = 20 ΩR3​ = 150 ΩR4​ = 250 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 12 V.

Vs = 12 VR1 = 400 ΩR2 = 20 ΩR3 = 150 ΩR4 = 250 Ω
Vab = V
3.Medium
+−2 V100 Ω100 Ω + ΔR100 Ω100 Ωab+−Vab​ = ?

A bridge has four 100 Ω arms and Vs = 2 V. The sensor R₂ increases by ΔR = 0.8 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 2 VR = 100 ΩΔR = 0.8 Ω
Vab = mV
4.Medium
+−6 V250 Ω250 Ω + ΔR250 Ω250 Ωab+−Vab​ = ?

A bridge has four 250 Ω arms and Vs = 6 V. The sensor R₂ increases by ΔR = 20 Ω. Find the exact output Vab in mV.

Vs = 6 VR = 250 ΩΔR = 20 Ω
Vab = mV
5.Hard
+−2.5 V350 Ω − ΔR350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 2.5 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 250 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2ε = 250 µε
Vo = mV
6.Hard
+−5 V120 Ω − ΔR120 Ω + ΔR120 Ω + ΔR120 Ω − ΔRab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2 and the strain is 800 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2ε = 800 µε
Vo = mV

Answer key

  1. 1. R4 = 750 Ω
  2. 2. Vab = −6.929 V
  3. 3. Vab = 4 mV
  4. 4. Vab = 115.4 mV
  5. 5. Vo = 0.625 mV
  6. 6. Vo = 8 mV

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