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 = 20 ΩR₂ = 50 ΩR₃ = 50 ΩR₄ = 500 Ω

V_ab = V

2.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 = 200 ΩR₂ = 150 ΩR₃ = 40 ΩR₄ = 1000 Ω

I_s = mA

3.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 12 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 12 VR₁ = 200 ΩR₂ = 120 ΩR₃ = 400 ΩR₄ = 200 ΩR_g = 500 Ω

I_g = µA

4.Medium

A bridge has four 400 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 100 Ω. Find the exact output V_ab in mV.

V_s = 15 VR = 400 ΩΔR = 100 Ω

V_ab = mV

5.Hard

A strain gauge (GF = 2) on a member with E = 110 GPa forms a quarter bridge excited with 10 V. The output reads 4 mV. Find the axial stress σ in MPa.

V_s = 10 VGF = 2V_o = 4 mVE = 110 GPa

σ = MPa

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2.5 mV/V at its rated load of 100 kg. It is excited with 5 V. Find its output V_o under a load of 80 kg.

2.5 mV/VF_rated = 100 kgV_s = 5 VF = 80 kg

V_o = mV

Answer key

1. V_ab = −1.948 V
2. I_s = 11.46 mA
3. I_g = 705.9 µA
4. V_ab = 833.3 mV
5. σ = 88 MPa
6. V_o = 10 mV

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