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​ = 100 ΩR2​ = 50 ΩR3​ = ?R4​ = 500 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 100 Ω, R₂ = 50 Ω and R₄ = 500 Ω. Find the setting R3.

R1 = 100 ΩR2 = 50 ΩR4 = 500 Ω
R3 = Ω
2.Easy
+−15 VR1​ = 800 ΩR2​ = 600 ΩR3​ = 500 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 800 Ω, R₂ = 600 Ω and R₃ = 500 Ω. Find the unknown resistor R4.

R1 = 800 ΩR2 = 600 ΩR3 = 500 Ω
R4 = Ω
3.Medium
+−2 V150 Ω150 Ω + ΔR150 Ω150 Ωab+−56.6 mV

A bridge with four 150 Ω arms is supplied with 2 V. When the sensor R₂ changes, the output reads Vab = 56.6 mV. Find the exact change ΔR of R₂.

Vs = 2 VR = 150 ΩVab = 56.6 mV
ΔR = Ω
4.Medium
+−3 V470 Ω470 Ω470 Ω470 Ωab+−

A 470 Ω strain gauge is one arm (R₂) of a bridge with four equal 470 Ω arms and an excitation of 3 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 3 VR = 470 Ω
Pg = mW
5.Hard
+−10 V120 Ω − ΔR120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 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 2.12 and the strain is 1200 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.12ε = 1200 µε
Vo = mV
6.Hard
+−5 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−3.844 mV

A strain gauge (GF = 2.05) on a member with E = 70 GPa forms a quarter bridge excited with 5 V. The output reads 3.844 mV. Find the axial stress σ in MPa.

Vs = 5 VGF = 2.05Vo = 3.844 mVE = 70 GPa
σ = MPa

Answer key

  1. 1. R3 = 1000 Ω
  2. 2. R4 = 375 Ω
  3. 3. ΔR = 18 Ω
  4. 4. Pg = 4.787 mW
  5. 5. Vo = 12.72 mV
  6. 6. σ = 105 MPa

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