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 = 200 Ω, R₂ = 120 Ω and R₃ = 200 Ω. Find the unknown resistor R₄.

R₁ = 200 ΩR₂ = 120 ΩR₃ = 200 Ω

R₄ = Ω

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 15 V.

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

V_ab = V

3.Medium

A 150 Ω strain gauge is one arm (R₂) of a bridge with four equal 150 Ω arms and an excitation of 10 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 10 VR = 150 Ω

P_g = mW

4.Medium

A bridge has four 300 Ω arms and V_s = 3 V. The sensor R₂ increases by ΔR = 60 Ω. Find the exact output V_ab in mV.

V_s = 3 VR = 300 ΩΔR = 60 Ω

V_ab = mV

5.Hard

A bridge with 1000 Ω arms is excited with 10 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.05 and the strain is 800 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.05ε = 800 µε

V_o = mV

6.Hard

A 350 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.14 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2ΔR = 0.14 Ω

ε = µε

Answer key

1. R₄ = 120 Ω
2. V_ab = 7.418 V
3. P_g = 166.7 mW
4. V_ab = 136.4 mV
5. V_o = 16.4 mV
6. ε = 200 µε

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