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​ = 500 ΩR2​ = 800 ΩR3​ = ?R4​ = 40 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 500 Ω, R₂ = 800 Ω and R₄ = 40 Ω. Find the setting R3.

R1 = 500 ΩR2 = 800 ΩR4 = 40 Ω
R3 = Ω
2.Easy
+−12 VR1​ = 500 ΩR2​ = 600 ΩR3​ = 800 ΩR4​ = ?abG0

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

R1 = 500 ΩR2 = 600 ΩR3 = 800 Ω
R4 = Ω
3.Medium
+−5 VR1​ = 300 ΩR2​ = 600 ΩR3​ = 600 ΩR4​ = 100 Ωab+−Rth​ = ?

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

Vs = 5 VR1 = 300 ΩR2 = 600 ΩR3 = 600 ΩR4 = 100 Ω
Rth = Ω
4.Medium
+−10 V400 Ω400 Ω400 Ω400 Ωab+−

A 400 Ω strain gauge is one arm (R₂) of a bridge with four equal 400 Ω arms and an excitation of 10 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 10 VR = 400 Ω
Pg = mW
5.Hard
+−2.5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 800 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2.05ε = 800 µε
Vo = mV
6.Hard
+−3 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2.12 and the strain is 600 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2.12ε = 600 µε
Vo = mV

Answer key

  1. 1. R3 = 25 Ω
  2. 2. R4 = 960 Ω
  3. 3. Rth = 285.7 Ω
  4. 4. Pg = 62.5 mW
  5. 5. Vo = 1.025 mV
  6. 6. Vo = 0.954 mV

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