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 by adjusting R₃. R₁ = 20 Ω, R₂ = 1000 Ω and R₄ = 120 Ω. Find the setting R₃.

R₁ = 20 ΩR₂ = 1000 ΩR₄ = 120 Ω

R₃ = Ω

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 9 V.

V_s = 9 VR₁ = 100 ΩR₂ = 800 ΩR₃ = 10 ΩR₄ = 120 Ω

V_ab = V

3.Medium

A bridge has four 250 Ω arms and V_s = 3 V. The sensor R₂ increases by ΔR = 0.5 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 3 VR = 250 ΩΔR = 0.5 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 = 15 VR₁ = 40 ΩR₂ = 120 ΩR₃ = 80 ΩR₄ = 120 Ω

R_th = Ω

5.Hard

A bridge with 350 Ω arms is excited with 5 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 200 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2ε = 200 µε

V_o = mV

6.Hard

A 350 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 0.5513 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2.1ΔR = 0.5513 Ω

ε = µε

Answer key

1. R₃ = 2.4 Ω
2. V_ab = −0.3077 V
3. V_ab = 1.5 mV
4. R_th = 78 Ω
5. V_o = 0.5 mV
6. ε = 750 µε

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