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 Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 100 Ω, R₂ = 80 Ω and R₃ = 60 Ω. Find the unknown resistor R₄.

R₁ = 100 ΩR₂ = 80 ΩR₃ = 60 Ω

R₄ = Ω

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 6 V.

V_s = 6 VR₁ = 300 ΩR₂ = 300 ΩR₃ = 10 ΩR₄ = 120 Ω

V_ab = V

3.Medium

A bridge has four 400 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 20 Ω. Find the exact output V_ab in mV.

V_s = 6 VR = 400 ΩΔR = 20 Ω

V_ab = mV

4.Medium

A bridge has four 470 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 1.88 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 6 VR = 470 ΩΔR = 1.88 Ω

V_ab = mV

5.Hard

A bridge with 120 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1500 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2ε = 1500 µε

V_o = mV

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 3 mV/V at its rated load of 500 kg. It is excited with 12 V. Find its output V_o under a load of 200 kg.

3 mV/VF_rated = 500 kgV_s = 12 VF = 200 kg

V_o = mV

Answer key

1. R₄ = 48 Ω
2. V_ab = −2.538 V
3. V_ab = 73.17 mV
4. V_ab = 6 mV
5. V_o = 1.875 mV
6. V_o = 14.4 mV

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