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​ = 50 ΩR2​ = 10 ΩR3​ = 20 ΩR4​ = 150 Ωab+−Vab​ = ?

Find the open-circuit output voltage Vab = Va − Vb of the bridge shown, with Vs = 2 V.

Vs = 2 VR1 = 50 ΩR2 = 10 ΩR3 = 20 ΩR4 = 150 Ω
Vab = V
2.Easy
2 ΩRₓBGACD40 cm

In a slide-wire (metre) bridge a known 2 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 40 cm from the left end A of the 100 cm wire. Find Rx.

R = 2 Ωl = 40 cmL = 100 cm
Rx = Ω
3.Medium
+−6 V100 Ω100 Ω100 Ω100 Ωab+−

A 100 Ω strain gauge is one arm (R₂) of a bridge with four equal 100 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 = 100 Ω
Pg = mW
4.Medium
+−12 VR1​ = 50 ΩR2​ = 100 ΩR3​ = 60 ΩR4​ = 20 ΩabGRg​ = 500 Ω

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (Vs = 12 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 12 VR1 = 50 ΩR2 = 100 ΩR3 = 60 ΩR4 = 20 ΩRg = 500 Ω
Ig = µA
5.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 200 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 = 2εmax = 200 µεVFS = 2.5 V
G =
6.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 2.05 and the strain is 500 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.05ε = 500 µε
Vo = mV

Answer key

  1. 1. Vab = −1.431 V
  2. 2. Rx = 3 Ω
  3. 3. Pg = 90 mW
  4. 4. Ig = 9119 µA
  5. 5. G = 8333
  6. 6. Vo = 5.125 mV

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