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
+−15 VR1​ = 250 ΩR2​ = 10 ΩR3​ = 10 ΩR4​ = 400 Ωab+−

The bridge shown is supplied with Vs = 15 V and its output is open. Find the current Is drawn from the supply, in mA.

Vs = 15 VR1 = 250 ΩR2 = 10 ΩR3 = 10 ΩR4 = 400 Ω
Is = mA
2.Easy
5 ΩRₓBGACD55 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 55 cm from the left end A of the 100 cm wire. Find Rx.

R = 5 Ωl = 55 cmL = 100 cm
Rx = Ω
3.Medium
+−3 VR1​ = 10 ΩR2​ = 800 ΩR3​ = 800 ΩR4​ = 120 ΩabGRg​ = 50 Ω

A galvanometer with a resistance of 50 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 = 10 ΩR2 = 800 ΩR3 = 800 ΩR4 = 120 ΩRg = 50 Ω
Ig = µA
4.Medium
+−9 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vab​ = ?

A bridge has four 120 Ω arms and Vs = 9 V. The sensor R₂ increases by ΔR = 12 Ω. Find the exact output Vab in mV.

Vs = 9 VR = 120 ΩΔR = 12 Ω
Vab = mV
5.Hard
+−5 V350 Ω − ΔR350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.1 and the strain is 1000 µε. Find the bridge output Vo in mV.

Vs = 5 VGF = 2.1ε = 1000 µε
Vo = mV
6.Hard
+−2.5 V350 Ω − ΔR350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 2.5 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 1200 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2.05ε = 1200 µε
Vo = mV

Answer key

  1. 1. Is = 94.28 mA
  2. 2. Rx = 4.091 Ω
  3. 3. Ig = 15659 µA
  4. 4. Vab = 214.3 mV
  5. 5. Vo = 5.25 mV
  6. 6. Vo = 3.075 mV

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