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​ = 1000 ΩR2​ = 800 ΩR3​ = 40 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 1000 Ω, R₂ = 800 Ω and R₃ = 40 Ω. Find the unknown resistor R4.

R1 = 1000 ΩR2 = 800 ΩR3 = 40 Ω
R4 = Ω
2.Easy
+−6 VR1​ = 200 ΩR2​ = 10 ΩR3​ = 600 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 200 Ω, R₂ = 10 Ω and R₃ = 600 Ω. Find the unknown resistor R4.

R1 = 200 ΩR2 = 10 ΩR3 = 600 Ω
R4 = Ω
3.Medium
+−15 V400 Ω400 Ω + ΔR400 Ω400 Ωab+−Vab​ = ?

A bridge has four 400 Ω arms and Vs = 15 V. The sensor R₂ increases by ΔR = 20 Ω. Find the exact output Vab in mV.

Vs = 15 VR = 400 ΩΔR = 20 Ω
Vab = mV
4.Medium
+−5 V200 Ω200 Ω200 Ω200 Ωab+−

A 200 Ω strain gauge is one arm (R₂) of a bridge with four equal 200 Ω arms and an excitation of 5 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 5 VR = 200 Ω
Pg = mW
5.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 =
6.Hard
+−V350 Ω350 Ω + ΔR350 Ω350 Ωab+−

A 350 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.35 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2ΔR = 0.35 Ω
ε = µε

Answer key

  1. 1. R4 = 32 Ω
  2. 2. R4 = 30 Ω
  3. 3. Vab = 182.9 mV
  4. 4. Pg = 31.25 mW
  5. 5. G = 5280
  6. 6. ε = 500 µε

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