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

In the bridge shown, V_s = 10 V, R₁ = 300 Ω and R₂ = 40 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 10 VR₁ = 300 ΩR₂ = 40 ΩR₃ = 500 ΩR₄ = 1000 Ω

V_a = V

2.Easy

In the bridge shown, V_s = 10 V, R₁ = 80 Ω and R₂ = 400 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 10 VR₁ = 80 ΩR₂ = 400 ΩR₃ = 1000 ΩR₄ = 200 Ω

V_a = V

3.Medium

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

V_s = 9 VR₁ = 800 ΩR₂ = 40 ΩR₃ = 250 ΩR₄ = 40 Ω

R_th = Ω

4.Medium

A bridge has four 1000 Ω arms and V_s = 3 V. The sensor R₂ increases by ΔR = 4 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 3 VR = 1000 ΩΔR = 4 Ω

V_ab = mV

5.Hard

A strain gauge (GF = 2.1) on a member with E = 200 GPa forms a quarter bridge excited with 3 V. The output reads 1.26 mV. Find the axial stress σ in MPa.

V_s = 3 VGF = 2.1V_o = 1.26 mVE = 200 GPa

σ = MPa

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 500 kg. It is excited with 12 V. Find its output V_o under a load of 375 kg.

2 mV/VF_rated = 500 kgV_s = 12 VF = 375 kg

V_o = mV

Answer key

1. V_a = 1.176 V
2. V_a = 8.333 V
3. R_th = 72.58 Ω
4. V_ab = 3 mV
5. σ = 160 MPa
6. V_o = 18 mV

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