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
+−5 VR1​ = 250 ΩR2​ = 200 ΩR3​ = 250 ΩR4​ = ?abG0

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 250 Ω, R₂ = 200 Ω and R₃ = 250 Ω. Find the unknown resistor R4.

R1 = 250 ΩR2 = 200 ΩR3 = 250 Ω
R4 = Ω
2.Easy
10 ΩRₓBGACD65 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 65 cm from the left end A of the 100 cm wire. Find Rx.

R = 10 Ωl = 65 cmL = 100 cm
Rx = Ω
3.Medium
+−5 V400 Ω400 Ω400 Ω400 Ωab+−

A 400 Ω strain gauge is one arm (R₂) of a bridge with four equal 400 Ω arms and an excitation of 5 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 5 VR = 400 Ω
Pg = mW
4.Medium
+−2 V470 Ω470 Ω470 Ω470 Ωab+−

A 470 Ω strain gauge is one arm (R₂) of a bridge with four equal 470 Ω arms and an excitation of 2 V. Find the power Pg dissipated in the gauge, in mW. Self-heating limits the excitation.

Vs = 2 VR = 470 Ω
Pg = mW
5.Hard
+−3 V350 Ω − ΔR350 Ω + ΔR350 Ω + ΔR350 Ω − ΔRab+−Vo​ = ?

A bridge with 350 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 750 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2.1ε = 750 µε
Vo = mV
6.Hard
+−10 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1000 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2ε = 1000 µε
Vo = mV

Answer key

  1. 1. R4 = 200 Ω
  2. 2. Rx = 5.385 Ω
  3. 3. Pg = 15.63 mW
  4. 4. Pg = 2.128 mW
  5. 5. Vo = 4.725 mV
  6. 6. Vo = 5 mV

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