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
+−10 VR1​ = 20 ΩR2​ = 120 ΩR3​ = 100 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 20 Ω, R₂ = 120 Ω and R₃ = 100 Ω. Find the unknown resistor R4.

R1 = 20 ΩR2 = 120 ΩR3 = 100 Ω
R4 = Ω
2.Easy
+−6 VR1​ = 40 ΩR2​ = 20 ΩR3​ = 300 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 40 Ω, R₂ = 20 Ω and R₃ = 300 Ω. Find the unknown resistor R4.

R1 = 40 ΩR2 = 20 ΩR3 = 300 Ω
R4 = Ω
3.Medium
+−2 V400 Ω400 Ω400 Ω400 Ωab+−

A 400 Ω strain gauge is one arm (R₂) of a bridge with four equal 400 Ω arms and an excitation of 2 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 2 VR = 400 Ω
Pg = mW
4.Medium
+−12 V150 Ω150 Ω + ΔR150 Ω150 Ωab+−Vab​ = ?

A bridge has four 150 Ω arms and Vs = 12 V. The sensor R₂ increases by ΔR = 12 Ω. Find the exact output Vab in mV.

Vs = 12 VR = 150 ΩΔR = 12 Ω
Vab = mV
5.Hard
+−V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−

A 1000 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 1.64 Ω. Find the strain ε in microstrain (µε).

R = 1000 ΩGF = 2.05ΔR = 1.64 Ω
ε = µε
6.Hard
+−2.5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2) is excited with 2.5 V. The largest strain to be measured is 500 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 2.5 VGF = 2εmax = 500 µεVFS = 3.3 V
G =

Answer key

  1. 1. R4 = 600 Ω
  2. 2. R4 = 150 Ω
  3. 3. Pg = 2.5 mW
  4. 4. Vab = 230.8 mV
  5. 5. ε = 800 µε
  6. 6. G = 5280

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