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
+−9 VR1​ = 250 ΩR2​ = 800 ΩR3​ = 400 ΩR4​ = 800 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 9 V.

Vs = 9 VR1 = 250 ΩR2 = 800 ΩR3 = 400 ΩR4 = 800 Ω
Vab = V
2.Easy
+−15 VR1​ = 200 ΩR2​ = 800 ΩR3​ = 10 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 200 Ω, R₂ = 800 Ω and R₃ = 10 Ω. Find the unknown resistor R4.

R1 = 200 ΩR2 = 800 ΩR3 = 10 Ω
R4 = Ω
3.Medium
+−12 V300 Ω300 Ω + ΔR300 Ω300 Ωab+−230.8 mV

A bridge with four 300 Ω arms is supplied with 12 V. When the sensor R₂ changes, the output reads Vab = 230.8 mV. Find the exact change ΔR of R₂.

Vs = 12 VR = 300 ΩVab = 230.8 mV
ΔR = Ω
4.Medium
+−12 VR1​ = 60 ΩR2​ = 100 ΩR3​ = 10 ΩR4​ = 800 ΩabGRg​ = 100 Ω

A galvanometer with a resistance of 100 Ω is connected between a and b of the bridge shown (Vs = 12 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 12 VR1 = 60 ΩR2 = 100 ΩR3 = 10 ΩR4 = 800 ΩRg = 100 Ω
Ig = µA
5.Hard
+−2.5 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−0.313 mV

A quarter bridge with one active gauge (GF = 2) is excited with 2.5 V. Under load the output reads 0.313 mV. Find the strain ε in µε.

Vs = 2.5 VGF = 2Vo = 0.313 mV
ε = µε
6.Hard
+−2.5 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−Vo​ = ?

A bridge with 1000 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1500 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2ε = 1500 µε
Vo = mV

Answer key

  1. 1. Vab = 0.8571 V
  2. 2. R4 = 40 Ω
  3. 3. ΔR = 24 Ω
  4. 4. Ig = −29529 µA
  5. 5. ε = 250.4 µε
  6. 6. Vo = 1.875 mV

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