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
+−2 VR1​ = 200 ΩR2​ = 120 ΩR3​ = ?R4​ = 60 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 200 Ω, R₂ = 120 Ω and R₄ = 60 Ω. Find the setting R3.

R1 = 200 ΩR2 = 120 ΩR4 = 60 Ω
R3 = Ω
2.Easy
20 ΩRₓBGACD30 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 30 cm from the left end A of the 100 cm wire. Find Rx.

R = 20 Ωl = 30 cmL = 100 cm
Rx = Ω
3.Medium
+−9 V470 Ω470 Ω + ΔR470 Ω470 Ωab+−254.7 mV

A bridge with four 470 Ω arms is supplied with 9 V. When the sensor R₂ changes, the output reads Vab = 254.7 mV. Find the exact change ΔR of R₂.

Vs = 9 VR = 470 ΩVab = 254.7 mV
ΔR = Ω
4.Medium
+−10 V300 Ω300 Ω300 Ω300 Ωab+−

A 300 Ω strain gauge is one arm (R₂) of a bridge with four equal 300 Ω arms and an excitation of 10 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 10 VR = 300 Ω
Pg = mW
5.Hard
+−2.5 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−1.922 mV

A quarter bridge with one active gauge (GF = 2.05) is excited with 2.5 V. Under load the output reads 1.922 mV. Find the strain ε in µε.

Vs = 2.5 VGF = 2.05Vo = 1.922 mV
ε = µε
6.Hard
+−12 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 mV/V at its rated load of 100 kg. It is excited with 12 V. Find its output Vo under a load of 25 kg.

1 mV/VFrated = 100 kgVs = 12 VF = 25 kg
Vo = mV

Answer key

  1. 1. R3 = 100 Ω
  2. 2. Rx = 46.67 Ω
  3. 3. ΔR = 56.4 Ω
  4. 4. Pg = 83.33 mW
  5. 5. ε = 1500 µε
  6. 6. Vo = 3 mV

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