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
+−6 VR1​ = 1000 ΩR2​ = 300 ΩR3​ = 800 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 1000 Ω, R₂ = 300 Ω and R₃ = 800 Ω. Find the unknown resistor R4.

R1 = 1000 ΩR2 = 300 ΩR3 = 800 Ω
R4 = Ω
2.Easy
+−5 VR1​ = 60 ΩR2​ = 150 ΩR3​ = ?R4​ = 60 ΩabG0

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

R1 = 60 ΩR2 = 150 ΩR4 = 60 Ω
R3 = Ω
3.Medium
+−9 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−254.7 mV

A bridge with four 1000 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 = 1000 ΩVab = 254.7 mV
ΔR = Ω
4.Medium
+−10 VR1​ = 100 ΩR2​ = 40 ΩR3​ = 600 ΩR4​ = 1000 ΩabGRg​ = 200 Ω

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (Vs = 10 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 10 VR1 = 100 ΩR2 = 40 ΩR3 = 600 ΩR4 = 1000 ΩRg = 200 Ω
Ig = µA
5.Hard
+−10 V120 Ω − ΔR120 Ω + ΔR120 Ω + ΔR120 Ω − ΔRab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 10 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.1 and the strain is 800 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.1ε = 800 µε
Vo = mV
6.Hard
+−5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−0.53 mV

A quarter bridge with one active gauge (GF = 2.12) is excited with 5 V. Under load the output reads 0.53 mV. Find the strain ε in µε.

Vs = 5 VGF = 2.12Vo = 0.53 mV
ε = µε

Answer key

  1. 1. R4 = 240 Ω
  2. 2. R3 = 24 Ω
  3. 3. ΔR = 120 Ω
  4. 4. Ig = −5621 µA
  5. 5. Vo = 16.8 mV
  6. 6. ε = 200 µε

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