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
+−15 VR1​ = 200 ΩR2​ = 50 ΩR3​ = 10 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 200 Ω, R₂ = 50 Ω and R₃ = 10 Ω. Find the unknown resistor R4.

R1 = 200 ΩR2 = 50 ΩR3 = 10 Ω
R4 = Ω
2.Easy
10 ΩRₓBGACD75 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 75 cm from the left end A of the 100 cm wire. Find Rx.

R = 10 Ωl = 75 cmL = 100 cm
Rx = Ω
3.Medium
+−15 V470 Ω470 Ω + ΔR470 Ω470 Ωab+−Vab​ = ?

A bridge has four 470 Ω arms and Vs = 15 V. The sensor R₂ increases by ΔR = 47 Ω. Find the exact output Vab in mV.

Vs = 15 VR = 470 ΩΔR = 47 Ω
Vab = mV
4.Medium
+−12 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vab​ = ?

A bridge has four 120 Ω arms and Vs = 12 V. The sensor R₂ increases by ΔR = 0.24 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 12 VR = 120 ΩΔR = 0.24 Ω
Vab = mV
5.Hard
+−5 V120 Ω − ΔR120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.05 and the strain is 200 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2.05ε = 200 µε
Vo = mV
6.Hard
+−5 V350 Ω − ΔR350 Ω + ΔR350 Ω + ΔR350 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 200 kg. It is excited with 5 V. Find its output Vo under a load of 150 kg.

1.5 mV/VFrated = 200 kgVs = 5 VF = 150 kg
Vo = mV

Answer key

  1. 1. R4 = 2.5 Ω
  2. 2. Rx = 3.333 Ω
  3. 3. Vab = 357.1 mV
  4. 4. Vab = 6 mV
  5. 5. Vo = 1.025 mV
  6. 6. Vo = 5.625 mV

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