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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 10 V.

V_s = 10 VR₁ = 150 ΩR₂ = 100 ΩR₃ = 400 ΩR₄ = 400 Ω

V_ab = V

2.Easy

The bridge shown is supplied with V_s = 6 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 6 VR₁ = 800 ΩR₂ = 500 ΩR₃ = 400 ΩR₄ = 80 Ω

I_s = mA

3.Medium

A bridge has four 100 Ω arms and V_s = 9 V. The sensor R₂ increases by ΔR = 0.2 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 9 VR = 100 ΩΔR = 0.2 Ω

V_ab = mV

4.Medium

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (V_s = 15 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 15 VR₁ = 1000 ΩR₂ = 50 ΩR₃ = 500 ΩR₄ = 80 ΩR_g = 200 Ω

I_g = µA

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1.5 mV/V at its rated load of 50 kg. It is excited with 5 V. Find its output V_o under a load of 12.5 kg.

1.5 mV/VF_rated = 50 kgV_s = 5 VF = 12.5 kg

V_o = mV

6.Hard

A strain gauge (GF = 2.1) on a member with E = 70 GPa forms a quarter bridge excited with 3 V. The output reads 0.945 mV. Find the axial stress σ in MPa.

V_s = 3 VGF = 2.1V_o = 0.945 mVE = 70 GPa

σ = MPa

Answer key

1. V_ab = −1 V
2. I_s = 17.12 mA
3. V_ab = 4.5 mV
4. I_g = −4279 µA
5. V_o = 1.875 mV
6. σ = 42 MPa

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