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​ = 10 ΩR2​ = 200 ΩR3​ = 120 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 10 Ω, R₂ = 200 Ω and R₃ = 120 Ω. Find the unknown resistor R4.

R1 = 10 ΩR2 = 200 ΩR3 = 120 Ω
R4 = Ω
2.Easy
+−15 VR1​ = 300 ΩR2​ = 100 ΩR3​ = 600 ΩR4​ = 150 Ωab+−

In the bridge shown, Vs = 15 V, R₁ = 300 Ω and R₂ = 100 Ω. Find the voltage Va of node a with respect to the negative supply rail.

Vs = 15 VR1 = 300 ΩR2 = 100 ΩR3 = 600 ΩR4 = 150 Ω
Va = V
3.Medium
+−3 V150 Ω150 Ω + ΔR150 Ω150 Ωab+−14.85 mV

A bridge with four 150 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads Vab = 14.85 mV. Find the exact change ΔR of R₂.

Vs = 3 VR = 150 ΩVab = 14.85 mV
ΔR = Ω
4.Medium
+−6 VR1​ = 50 ΩR2​ = 60 ΩR3​ = 50 ΩR4​ = 500 ΩabGRg​ = 20 Ω

A galvanometer with a resistance of 20 Ω is connected between a and b of the bridge shown (Vs = 6 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 6 VR1 = 50 ΩR2 = 60 ΩR3 = 50 ΩR4 = 500 ΩRg = 20 Ω
Ig = µA
5.Hard
+−2.5 V120 Ω − ΔR120 Ω + ΔR120 Ω + ΔR120 Ω − ΔRab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 2.5 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 1500 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2.1ε = 1500 µε
Vo = mV
6.Hard
+−2.5 V120 Ω − ΔR120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 2.5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.05 and the strain is 750 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2.05ε = 750 µε
Vo = mV

Answer key

  1. 1. R4 = 2400 Ω
  2. 2. Va = 3.75 V
  3. 3. ΔR = 3 Ω
  4. 4. Ig = −23529 µA
  5. 5. Vo = 7.875 mV
  6. 6. Vo = 1.922 mV

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