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​ = 800 ΩR2​ = 400 ΩR3​ = 250 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 800 Ω, R₂ = 400 Ω and R₃ = 250 Ω. Find the unknown resistor R4.

R1 = 800 ΩR2 = 400 ΩR3 = 250 Ω
R4 = Ω
2.Easy
+−12 VR1​ = 300 ΩR2​ = 60 ΩR3​ = 10 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 300 Ω, R₂ = 60 Ω and R₃ = 10 Ω. Find the unknown resistor R4.

R1 = 300 ΩR2 = 60 ΩR3 = 10 Ω
R4 = Ω
3.Medium
+−2 VR1​ = 100 ΩR2​ = 120 ΩR3​ = 40 ΩR4​ = 60 Ωab+−Rth​ = ?

Find the Thévenin resistance Rth of the bridge shown, seen from the output terminals a and b.

Vs = 2 VR1 = 100 ΩR2 = 120 ΩR3 = 40 ΩR4 = 60 Ω
Rth = Ω
4.Medium
+−6 V500 Ω500 Ω500 Ω500 Ωab+−

A 500 Ω strain gauge is one arm (R₂) of a bridge with four equal 500 Ω arms and an excitation of 6 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 6 VR = 500 Ω
Pg = mW
5.Hard
+−5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−3.975 mV

A quarter bridge with one active gauge (GF = 2.12) is excited with 5 V. Under load the output reads 3.975 mV. Find the strain ε in µε.

Vs = 5 VGF = 2.12Vo = 3.975 mV
ε = µε
6.Hard
+−3 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2.1) is excited with 3 V. The largest strain to be measured is 750 µε, and it must give 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 3 VGF = 2.1εmax = 750 µεVFS = 2.5 V
G =

Answer key

  1. 1. R4 = 125 Ω
  2. 2. R4 = 2 Ω
  3. 3. Rth = 78.55 Ω
  4. 4. Pg = 18 mW
  5. 5. ε = 1500 µε
  6. 6. G = 2116

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