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
20 ΩRₓBGACD80 cm

In a slide-wire (metre) bridge a known 20 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 80 cm from the left end A of the 100 cm wire. Find Rx.

R = 20 Ωl = 80 cmL = 100 cm
Rx = Ω
2.Easy
10 ΩRₓBGACD60 cm

In a slide-wire (metre) bridge a known 10 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 60 cm from the left end A of the 100 cm wire. Find Rx.

R = 10 Ωl = 60 cmL = 100 cm
Rx = Ω
3.Medium
+−5 VR1​ = 200 ΩR2​ = 150 ΩR3​ = 600 ΩR4​ = 150 ΩabGRg​ = 20 Ω

A galvanometer with a resistance of 20 Ω is connected between a and b of the bridge shown (Vs = 5 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 5 VR1 = 200 ΩR2 = 150 ΩR3 = 600 ΩR4 = 150 ΩRg = 20 Ω
Ig = µA
4.Medium
+−12 V150 Ω150 Ω + ΔR150 Ω150 Ωab+−Vab​ = ?

A bridge has four 150 Ω arms and Vs = 12 V. The sensor R₂ increases by ΔR = 7.5 Ω. Find the exact output Vab in mV.

Vs = 12 VR = 150 ΩΔR = 7.5 Ω
Vab = mV
5.Hard
+−3 V120 Ω − ΔR120 Ω + ΔR120 Ω + ΔR120 Ω − ΔRab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 3 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.1 and the strain is 400 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2.1ε = 400 µε
Vo = mV
6.Hard
+−3 V120 Ω − ΔR120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 3 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 1500 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2.12ε = 1500 µε
Vo = mV

Answer key

  1. 1. Rx = 5 Ω
  2. 2. Rx = 6.667 Ω
  3. 3. Ig = 5063 µA
  4. 4. Vab = 146.3 mV
  5. 5. Vo = 2.52 mV
  6. 6. Vo = 4.77 mV

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