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
+−12 VR1​ = 10 ΩR2​ = 10 ΩR3​ = 600 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 10 Ω, R₂ = 10 Ω and R₃ = 600 Ω. Find the unknown resistor R4.

R1 = 10 ΩR2 = 10 ΩR3 = 600 Ω
R4 = Ω
2.Easy
+−9 VR1​ = 40 ΩR2​ = 120 ΩR3​ = 20 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 40 Ω, R₂ = 120 Ω and R₃ = 20 Ω. Find the unknown resistor R4.

R1 = 40 ΩR2 = 120 ΩR3 = 20 Ω
R4 = Ω
3.Medium
+−12 V100 Ω100 Ω + ΔR100 Ω100 Ωab+−339.6 mV

A bridge with four 100 Ω arms is supplied with 12 V. When the sensor R₂ changes, the output reads Vab = 339.6 mV. Find the exact change ΔR of R₂.

Vs = 12 VR = 100 ΩVab = 339.6 mV
ΔR = Ω
4.Medium
+−3 V330 Ω330 Ω + ΔR330 Ω330 Ωab+−Vab​ = ?

A bridge has four 330 Ω arms and Vs = 3 V. The sensor R₂ increases by ΔR = 66 Ω. Find the exact output Vab in mV.

Vs = 3 VR = 330 ΩΔR = 66 Ω
Vab = mV
5.Hard
+−10 V120 Ω − ΔR120 Ω + ΔR120 Ω + ΔR120 Ω − ΔRab+−Vo​ = ?

A load cell (a full bridge of strain gauges) has a rated output of 1.5 mV/V at its rated load of 500 kg. It is excited with 10 V. Find its output Vo under a load of 250 kg.

1.5 mV/VFrated = 500 kgVs = 10 VF = 250 kg
Vo = mV
6.Hard
+−10 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−Vo​ = ?

A bridge with 1000 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2.1 and the strain is 1500 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.1ε = 1500 µε
Vo = mV

Answer key

  1. 1. R4 = 600 Ω
  2. 2. R4 = 60 Ω
  3. 3. ΔR = 12 Ω
  4. 4. Vab = 136.4 mV
  5. 5. Vo = 7.5 mV
  6. 6. Vo = 7.875 mV

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