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 = 3 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 3 VR₁ = 100 ΩR₂ = 120 ΩR₃ = 250 ΩR₄ = 120 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 60 Ω, R₂ = 10 Ω and R₃ = 600 Ω. Find the unknown resistor R₄.

R₁ = 60 ΩR₂ = 10 ΩR₃ = 600 Ω

R₄ = Ω

3.Medium

A 500 Ω strain gauge is one arm (R₂) of a bridge with four equal 500 Ω arms and an excitation of 3 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 3 VR = 500 Ω

P_g = mW

4.Medium

A bridge with four 400 Ω arms is supplied with 15 V. When the sensor R₂ changes, the output reads V_ab = 74.26 mV. Find the exact change ΔR of R₂.

V_s = 15 VR = 400 ΩV_ab = 74.26 mV

ΔR = Ω

5.Hard

A bridge with 120 Ω arms is excited with 5 V and has one active gauge (quarter bridge). The gauge factor is 2.12 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2.12ε = 1000 µε

V_o = mV

6.Hard

A strain gauge (GF = 2.12) on a member with E = 200 GPa forms a quarter bridge excited with 5 V. The output reads 2.12 mV. Find the axial stress σ in MPa.

V_s = 5 VGF = 2.12V_o = 2.12 mVE = 200 GPa

σ = MPa

Answer key

1. I_s = 21.74 mA
2. R₄ = 100 Ω
3. P_g = 4.5 mW
4. ΔR = 8 Ω
5. V_o = 2.65 mV
6. σ = 160 MPa

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