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​ = 80 ΩR2​ = 500 ΩR3​ = ?R4​ = 10 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 80 Ω, R₂ = 500 Ω and R₄ = 10 Ω. Find the setting R3.

R1 = 80 ΩR2 = 500 ΩR4 = 10 Ω
R3 = Ω
2.Easy
+−10 VR1​ = 150 ΩR2​ = 40 ΩR3​ = ?R4​ = 50 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 150 Ω, R₂ = 40 Ω and R₄ = 50 Ω. Find the setting R3.

R1 = 150 ΩR2 = 40 ΩR4 = 50 Ω
R3 = Ω
3.Medium
+−10 V470 Ω470 Ω470 Ω470 Ωab+−

A 470 Ω strain gauge is one arm (R₂) of a bridge with four equal 470 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 = 470 Ω
Pg = mW
4.Medium
+−12 VR1​ = 400 ΩR2​ = 200 ΩR3​ = 100 ΩR4​ = 20 ΩabGRg​ = 50 Ω

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (Vs = 12 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 12 VR1 = 400 ΩR2 = 200 ΩR3 = 100 ΩR4 = 20 ΩRg = 50 Ω
Ig = µA
5.Hard
+−5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2.05) is excited with 5 V. The largest strain to be measured is 250 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 5 VGF = 2.05εmax = 250 µεVFS = 5 V
G =
6.Hard
+−10 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1000 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2ε = 1000 µε
Vo = mV

Answer key

  1. 1. R3 = 1.6 Ω
  2. 2. R3 = 187.5 Ω
  3. 3. Pg = 53.19 mW
  4. 4. Ig = 10000 µA
  5. 5. G = 7805
  6. 6. Vo = 5 mV

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