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​ = 60 ΩR2​ = 150 ΩR3​ = ?R4​ = 600 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 60 Ω, R₂ = 150 Ω and R₄ = 600 Ω. Find the setting R3.

R1 = 60 ΩR2 = 150 ΩR4 = 600 Ω
R3 = Ω
2.Easy
100 ΩRₓBGACD20 cm

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

R = 100 Ωl = 20 cmL = 100 cm
Rx = Ω
3.Medium
+−5 V1000 Ω1000 Ω1000 Ω1000 Ωab+−

A 1000 Ω strain gauge is one arm (R₂) of a bridge with four equal 1000 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 = 1000 Ω
Pg = mW
4.Medium
+−10 V330 Ω330 Ω330 Ω330 Ωab+−

A 330 Ω strain gauge is one arm (R₂) of a bridge with four equal 330 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 = 330 Ω
Pg = mW
5.Hard
+−2.5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2.1) is excited with 2.5 V. The largest strain to be measured is 600 µε, and it must give 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 2.5 VGF = 2.1εmax = 600 µεVFS = 2.5 V
G =
6.Hard
+−V350 Ω350 Ω + ΔR350 Ω350 Ωab+−

A 350 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.861 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2.05ΔR = 0.861 Ω
ε = µε

Answer key

  1. 1. R3 = 240 Ω
  2. 2. Rx = 400 Ω
  3. 3. Pg = 6.25 mW
  4. 4. Pg = 75.76 mW
  5. 5. G = 3175
  6. 6. ε = 1200 µε

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