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
+−5 VR1​ = 50 ΩR2​ = 40 ΩR3​ = 150 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 50 Ω, R₂ = 40 Ω and R₃ = 150 Ω. Find the unknown resistor R4.

R1 = 50 ΩR2 = 40 ΩR3 = 150 Ω
R4 = Ω
2.Easy
+−12 VR1​ = 50 ΩR2​ = 400 ΩR3​ = ?R4​ = 200 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 50 Ω, R₂ = 400 Ω and R₄ = 200 Ω. Find the setting R3.

R1 = 50 ΩR2 = 400 ΩR4 = 200 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
+−10 V330 Ω330 Ω + ΔR330 Ω330 Ωab+−98.04 mV

A bridge with four 330 Ω arms is supplied with 10 V. When the sensor R₂ changes, the output reads Vab = 98.04 mV. Find the exact change ΔR of R₂.

Vs = 10 VR = 330 ΩVab = 98.04 mV
ΔR = Ω
5.Hard
+−10 V120 Ω − ΔR120 Ω + ΔR120 Ω + ΔR120 Ω − ΔRab+−Vo​ = ?

A load cell (a full bridge of strain gauges) has a rated output of 3 mV/V at its rated load of 50 kg. It is excited with 10 V. Find its output Vo under a load of 40 kg.

3 mV/VFrated = 50 kgVs = 10 VF = 40 kg
Vo = mV
6.Hard
+−12 V350 Ω − ΔR350 Ω + ΔR350 Ω + ΔR350 Ω − ΔRab+−Vo​ = ?

A load cell (a full bridge of strain gauges) has a rated output of 2.5 mV/V at its rated load of 50 kg. It is excited with 12 V. Find its output Vo under a load of 10 kg.

2.5 mV/VFrated = 50 kgVs = 12 VF = 10 kg
Vo = mV

Answer key

  1. 1. R4 = 120 Ω
  2. 2. R3 = 25 Ω
  3. 3. Pg = 53.19 mW
  4. 4. ΔR = 13.2 Ω
  5. 5. Vo = 24 mV
  6. 6. Vo = 6 mV

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