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

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 1000 Ω, R₂ = 800 Ω and R₃ = 10 Ω. Find the unknown resistor R₄.

R₁ = 1000 ΩR₂ = 800 ΩR₃ = 10 Ω

R₄ = Ω

2.Easy

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

V_s = 15 VR₁ = 150 ΩR₂ = 600 ΩR₃ = 20 ΩR₄ = 1000 Ω

I_s = mA

3.Medium

A bridge has four 350 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 70 Ω. Find the exact output V_ab in mV.

V_s = 2 VR = 350 ΩΔR = 70 Ω

V_ab = mV

4.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 6 VR₁ = 10 ΩR₂ = 20 ΩR₃ = 500 ΩR₄ = 50 Ω

R_th = Ω

5.Hard

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 and the strain is 400 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2ε = 400 µε

V_o = mV

6.Hard

A strain gauge (GF = 2.12) on a member with E = 70 GPa forms a quarter bridge excited with 10 V. The output reads 2.65 mV. Find the axial stress σ in MPa.

V_s = 10 VGF = 2.12V_o = 2.65 mVE = 70 GPa

σ = MPa

Answer key

1. R₄ = 8 Ω
2. I_s = 34.71 mA
3. V_ab = 90.91 mV
4. R_th = 52.12 Ω
5. V_o = 2 mV
6. σ = 35 MPa

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