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 bridge shown is supplied with V_s = 12 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 12 VR₁ = 10 ΩR₂ = 100 ΩR₃ = 250 ΩR₄ = 80 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 150 Ω, R₂ = 600 Ω and R₄ = 250 Ω. Find the setting R₃.

R₁ = 150 ΩR₂ = 600 ΩR₄ = 250 Ω

R₃ = Ω

3.Medium

A 120 Ω strain gauge is one arm (R₂) of a bridge with four equal 120 Ω arms and an excitation of 2 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 2 VR = 120 Ω

P_g = mW

4.Medium

A bridge has four 120 Ω arms and V_s = 10 V. The sensor R₂ increases by ΔR = 0.24 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 10 VR = 120 ΩΔR = 0.24 Ω

V_ab = mV

5.Hard

A quarter bridge with one active gauge (GF = 2) is excited with 5 V. Under load the output reads 1.5 mV. Find the strain ε in µε.

V_s = 5 VGF = 2V_o = 1.5 mV

ε = µε

6.Hard

A bridge with 120 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 2.12 and the strain is 1500 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.12ε = 1500 µε

V_o = mV

Answer key

1. I_s = 145.5 mA
2. R₃ = 62.5 Ω
3. P_g = 8.333 mW
4. V_ab = 5 mV
5. ε = 600 µε
6. V_o = 31.8 mV

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