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​ = 800 ΩR2​ = 200 ΩR3​ = 60 ΩR4​ = 80 Ωab+−

The bridge shown is supplied with Vs = 2 V and its output is open. Find the current Is drawn from the supply, in mA.

Vs = 2 VR1 = 800 ΩR2 = 200 ΩR3 = 60 ΩR4 = 80 Ω
Is = mA
2.Easy
5 ΩRₓBGACD45 cm

In a slide-wire (metre) bridge a known 5 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 45 cm from the left end A of the 100 cm wire. Find Rx.

R = 5 Ωl = 45 cmL = 100 cm
Rx = Ω
3.Medium
+−2 V100 Ω100 Ω + ΔR100 Ω100 Ωab+−Vab​ = ?

A bridge has four 100 Ω arms and Vs = 2 V. The sensor R₂ increases by ΔR = 0.5 Ω. Using the small-change approximation, find the output Vab in mV.

Vs = 2 VR = 100 ΩΔR = 0.5 Ω
Vab = mV
4.Medium
+−3 VR1​ = 60 ΩR2​ = 120 ΩR3​ = 250 ΩR4​ = 1000 ΩabGRg​ = 200 Ω

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (Vs = 3 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 3 VR1 = 60 ΩR2 = 120 ΩR3 = 250 ΩR4 = 1000 ΩRg = 200 Ω
Ig = µA
5.Hard
+−10 V120 Ω − ΔR120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 10 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.12 and the strain is 500 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.12ε = 500 µε
Vo = mV
6.Hard
+−3 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​

A quarter bridge (one active gauge, GF = 2) is excited with 3 V. The largest strain to be measured is 1000 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

Vs = 3 VGF = 2εmax = 1000 µεVFS = 5 V
G =

Answer key

  1. 1. Is = 16.29 mA
  2. 2. Rx = 6.111 Ω
  3. 3. Vab = 2.5 mV
  4. 4. Ig = −909.1 µA
  5. 5. Vo = 5.3 mV
  6. 6. G = 3333

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