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
+−2 VR1​ = 50 ΩR2​ = 400 ΩR3​ = ?R4​ = 20 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 50 Ω, R₂ = 400 Ω and R₄ = 20 Ω. Find the setting R3.

R1 = 50 ΩR2 = 400 ΩR4 = 20 Ω
R3 = Ω
2.Easy
+−6 VR1​ = 200 ΩR2​ = 800 ΩR3​ = 120 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 200 Ω, R₂ = 800 Ω and R₃ = 120 Ω. Find the unknown resistor R4.

R1 = 200 ΩR2 = 800 ΩR3 = 120 Ω
R4 = Ω
3.Medium
+−3 V100 Ω100 Ω + ΔR100 Ω100 Ωab+−71.43 mV

A bridge with four 100 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads Vab = 71.43 mV. Find the exact change ΔR of R₂.

Vs = 3 VR = 100 ΩVab = 71.43 mV
ΔR = Ω
4.Medium
+−10 VR1​ = 800 ΩR2​ = 20 ΩR3​ = 600 ΩR4​ = 300 Ωab+−Rth​ = ?

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

Vs = 10 VR1 = 800 ΩR2 = 20 ΩR3 = 600 ΩR4 = 300 Ω
Rth = Ω
5.Hard
+−10 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−1.05 mV

A quarter bridge with one active gauge (GF = 2.1) is excited with 10 V. Under load the output reads 1.05 mV. Find the strain ε in µε.

Vs = 10 VGF = 2.1Vo = 1.05 mV
ε = µε
6.Hard
+−5 V350 Ω − ΔR350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 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 2.05 and the strain is 1200 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2.05ε = 1200 µε
Vo = mV

Answer key

  1. 1. R3 = 2.5 Ω
  2. 2. R4 = 480 Ω
  3. 3. ΔR = 10 Ω
  4. 4. Rth = 219.5 Ω
  5. 5. ε = 200 µε
  6. 6. Vo = 6.15 mV

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