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
10 ΩRₓBGACD25 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 25 cm from the left end A of the 100 cm wire. Find Rx.

R = 10 Ωl = 25 cmL = 100 cm
Rx = Ω
2.Easy
+−6 VR1​ = 600 ΩR2​ = 300 ΩR3​ = ?R4​ = 800 ΩabG0

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 600 Ω, R₂ = 300 Ω and R₄ = 800 Ω. Find the setting R3.

R1 = 600 ΩR2 = 300 ΩR4 = 800 Ω
R3 = Ω
3.Medium
+−12 VR1​ = 120 ΩR2​ = 200 ΩR3​ = 100 ΩR4​ = 10 ΩabGRg​ = 50 Ω

A galvanometer with a resistance of 50 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 = 120 ΩR2 = 200 ΩR3 = 100 ΩR4 = 10 ΩRg = 50 Ω
Ig = µA
4.Medium
+−5 VR1​ = 120 ΩR2​ = 10 ΩR3​ = 40 ΩR4​ = 400 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 = 120 ΩR2 = 10 ΩR3 = 40 ΩR4 = 400 ΩRg = 20 Ω
Ig = µA
5.Hard
+−10 V120 Ω120 Ω + ΔR120 Ω120 Ωab+−Vo​ = ?

A bridge with 120 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2.12 and the strain is 600 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.12ε = 600 µε
Vo = mV
6.Hard
+−2.5 V1000 Ω − ΔR1000 Ω + ΔR1000 Ω1000 Ωab+−Vo​ = ?

A bridge with 1000 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 1000 µε. Find the bridge output Vo in mV.

Vs = 2.5 VGF = 2.05ε = 1000 µε
Vo = mV

Answer key

  1. 1. Rx = 30 Ω
  2. 2. R3 = 1600 Ω
  3. 3. Ig = 47797 µA
  4. 4. Ig = −63433 µA
  5. 5. Vo = 3.18 mV
  6. 6. Vo = 2.563 mV

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