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​ = 150 ΩR2​ = 800 ΩR3​ = 150 ΩR4​ = 600 Ωab+−Vab​ = ?

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

Vs = 9 VR1 = 150 ΩR2 = 800 ΩR3 = 150 ΩR4 = 600 Ω
Vab = V
2.Easy
10 ΩRₓBGACD60 cm

In a slide-wire (metre) bridge a known 10 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 60 cm from the left end A of the 100 cm wire. Find Rx.

R = 10 Ωl = 60 cmL = 100 cm
Rx = Ω
3.Medium
+−12 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−146.3 mV

A bridge with four 120 Ω arms is supplied with 12 V. When the sensor R₂ changes, the output reads Vab = 146.3 mV. Find the exact change ΔR of R₂.

Vs = 12 VR = 120 ΩVab = 146.3 mV
ΔR = Ω
4.Medium
+−6 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vab​ = ?

A bridge has four 350 Ω arms and Vs = 6 V. The sensor R₂ increases by ΔR = 3.5 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 6 VR = 350 ΩΔR = 3.5 Ω
Vab = mV
5.Hard
+−3 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−0.9 mV

A quarter bridge with one active gauge (GF = 2) is excited with 3 V. Under load the output reads 0.9 mV. Find the strain ε in µε.

Vs = 3 VGF = 2Vo = 0.9 mV
ε = µε
6.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 50 kg. It is excited with 10 V. Find its output Vo under a load of 20 kg.

1.5 mV/VFrated = 50 kgVs = 10 VF = 20 kg
Vo = mV

Answer key

  1. 1. Vab = 0.3789 V
  2. 2. Rx = 6.667 Ω
  3. 3. ΔR = 6 Ω
  4. 4. Vab = 15 mV
  5. 5. ε = 600 µε
  6. 6. Vo = 6 mV

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