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
+−3 VR1​ = 1000 ΩR2​ = 150 ΩR3​ = 300 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 1000 Ω, R₂ = 150 Ω and R₃ = 300 Ω. Find the unknown resistor R4.

R1 = 1000 ΩR2 = 150 ΩR3 = 300 Ω
R4 = Ω
2.Easy
+−10 VR1​ = 200 ΩR2​ = 40 ΩR3​ = ?R4​ = 150 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 200 Ω, R₂ = 40 Ω and R₄ = 150 Ω. Find the setting R3.

R1 = 200 ΩR2 = 40 ΩR4 = 150 Ω
R3 = Ω
3.Medium
+−3 V150 Ω150 Ω + ΔR150 Ω150 Ωab+−Vab​ = ?

A bridge has four 150 Ω arms and Vs = 3 V. The sensor R₂ increases by ΔR = 30 Ω. Find the exact output Vab in mV.

Vs = 3 VR = 150 ΩΔR = 30 Ω
Vab = mV
4.Medium
+−2 VR1​ = 120 ΩR2​ = 250 ΩR3​ = 120 ΩR4​ = 40 ΩabGRg​ = 200 Ω

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (Vs = 2 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 2 VR1 = 120 ΩR2 = 250 ΩR3 = 120 ΩR4 = 40 ΩRg = 200 Ω
Ig = µA
5.Hard
+−2.5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−1.06 mV

A quarter bridge with one active gauge (GF = 2.12) is excited with 2.5 V. Under load the output reads 1.06 mV. Find the strain ε in µε.

Vs = 2.5 VGF = 2.12Vo = 1.06 mV
ε = µε
6.Hard
+−3 V120 Ω − ΔR120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 3 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.1 and the strain is 800 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2.1ε = 800 µε
Vo = mV

Answer key

  1. 1. R4 = 45 Ω
  2. 2. R3 = 750 Ω
  3. 3. Vab = 136.4 mV
  4. 4. Ig = 2737 µA
  5. 5. ε = 800 µε
  6. 6. Vo = 2.52 mV

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