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​ = 400 ΩR2​ = 120 ΩR3​ = 50 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 400 Ω, R₂ = 120 Ω and R₃ = 50 Ω. Find the unknown resistor R4.

R1 = 400 ΩR2 = 120 ΩR3 = 50 Ω
R4 = Ω
2.Easy
+−6 VR1​ = 100 ΩR2​ = 120 ΩR3​ = 50 ΩR4​ = 250 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 6 V.

Vs = 6 VR1 = 100 ΩR2 = 120 ΩR3 = 50 ΩR4 = 250 Ω
Vab = V
3.Medium
+−5 V300 Ω300 Ω + ΔR300 Ω300 Ωab+−Vab​ = ?

A bridge has four 300 Ω arms and Vs = 5 V. The sensor R₂ increases by ΔR = 2.4 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 5 VR = 300 ΩΔR = 2.4 Ω
Vab = mV
4.Medium
+−15 V400 Ω400 Ω + ΔR400 Ω400 Ωab+−147.1 mV

A bridge with four 400 Ω arms is supplied with 15 V. When the sensor R₂ changes, the output reads Vab = 147.1 mV. Find the exact change ΔR of R₂.

Vs = 15 VR = 400 ΩVab = 147.1 mV
ΔR = Ω
5.Hard
+−10 V1000 Ω − ΔR1000 Ω + ΔR1000 Ω + ΔR1000 Ω − ΔRab+−Vo​ = ?

A bridge with 1000 Ω arms is excited with 10 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.05 and the strain is 1000 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.05ε = 1000 µε
Vo = mV
6.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 200 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2ε = 200 µε
Vo = mV

Answer key

  1. 1. R4 = 15 Ω
  2. 2. Vab = −1.727 V
  3. 3. Vab = 10 mV
  4. 4. ΔR = 16 Ω
  5. 5. Vo = 20.5 mV
  6. 6. Vo = 0.5 mV

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