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​ = 150 ΩR2​ = 20 ΩR3​ = ?R4​ = 150 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 150 Ω, R₂ = 20 Ω and R₄ = 150 Ω. Find the setting R3.

R1 = 150 ΩR2 = 20 ΩR4 = 150 Ω
R3 = Ω
2.Easy
20 ΩRₓBGACD45 cm

In a slide-wire (metre) bridge a known 20 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 45 cm from the left end A of the 100 cm wire. Find Rx.

R = 20 Ωl = 45 cmL = 100 cm
Rx = Ω
3.Medium
+−5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vab​ = ?

A bridge has four 350 Ω arms and Vs = 5 V. The sensor R₂ increases by ΔR = 1.75 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 5 VR = 350 ΩΔR = 1.75 Ω
Vab = mV
4.Medium
+−5 VR1​ = 60 ΩR2​ = 100 ΩR3​ = 60 ΩR4​ = 60 ΩabGRg​ = 100 Ω

A galvanometer with a resistance of 100 Ω is connected between a and b of the bridge shown (Vs = 5 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 5 VR1 = 60 ΩR2 = 100 ΩR3 = 60 ΩR4 = 60 ΩRg = 100 Ω
Ig = µA
5.Hard
+−2.5 V350 Ω − ΔR350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 2.5 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 600 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2.1ε = 600 µε
Vo = mV
6.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 2.12 and the strain is 600 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2.12ε = 600 µε
Vo = mV

Answer key

  1. 1. R3 = 1125 Ω
  2. 2. Rx = 24.44 Ω
  3. 3. Vab = 6.25 mV
  4. 4. Ig = 3731 µA
  5. 5. Vo = 1.575 mV
  6. 6. Vo = 3.18 mV

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