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​ = 40 ΩR2​ = 40 ΩR3​ = 10 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 40 Ω, R₂ = 40 Ω and R₃ = 10 Ω. Find the unknown resistor R4.

R1 = 40 ΩR2 = 40 ΩR3 = 10 Ω
R4 = Ω
2.Easy
+−15 VR1​ = 80 ΩR2​ = 10 ΩR3​ = ?R4​ = 50 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 80 Ω, R₂ = 10 Ω and R₄ = 50 Ω. Find the setting R3.

R1 = 80 ΩR2 = 10 ΩR4 = 50 Ω
R3 = Ω
3.Medium
+−6 V330 Ω330 Ω + ΔR330 Ω330 Ωab+−142.9 mV

A bridge with four 330 Ω arms is supplied with 6 V. When the sensor R₂ changes, the output reads Vab = 142.9 mV. Find the exact change ΔR of R₂.

Vs = 6 VR = 330 ΩVab = 142.9 mV
ΔR = Ω
4.Medium
+−15 VR1​ = 200 ΩR2​ = 800 ΩR3​ = 500 ΩR4​ = 80 ΩabGRg​ = 200 Ω

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (Vs = 15 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 15 VR1 = 200 ΩR2 = 800 ΩR3 = 500 ΩR4 = 80 ΩRg = 200 Ω
Ig = µA
5.Hard
+−2.5 V1000 Ω1000 Ω + ΔR1000 Ω1000 Ωab+−Vo​ = ?

A bridge with 1000 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2.1 and the strain is 750 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2.1ε = 750 µε
Vo = mV
6.Hard
+−2.5 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2) is excited with 2.5 V. The largest strain to be measured is 400 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 2.5 VGF = 2εmax = 400 µεVFS = 5 V
G =

Answer key

  1. 1. R4 = 10 Ω
  2. 2. R3 = 400 Ω
  3. 3. ΔR = 33 Ω
  4. 4. Ig = 23151 µA
  5. 5. Vo = 0.9844 mV
  6. 6. G = 10000

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