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 by adjusting R₃. R₁ = 60 Ω, R₂ = 100 Ω and R₄ = 200 Ω. Find the setting R₃.

R₁ = 60 ΩR₂ = 100 ΩR₄ = 200 Ω

R₃ = Ω

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 3 V.

V_s = 3 VR₁ = 120 ΩR₂ = 40 ΩR₃ = 400 ΩR₄ = 150 Ω

V_ab = V

3.Medium

A galvanometer with a resistance of 100 Ω is connected between a and b of the bridge shown (V_s = 2 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 2 VR₁ = 200 ΩR₂ = 600 ΩR₃ = 10 ΩR₄ = 100 ΩR_g = 100 Ω

I_g = µA

4.Medium

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

V_s = 12 VR₁ = 800 ΩR₂ = 100 ΩR₃ = 120 ΩR₄ = 120 Ω

R_th = Ω

5.Hard

A bridge with 350 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.05ε = 1000 µε

V_o = mV

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1 mV/V at its rated load of 500 kg. It is excited with 10 V. Find its output V_o under a load of 375 kg.

1 mV/VF_rated = 500 kgV_s = 10 VF = 375 kg

V_o = mV

Answer key

1. R₃ = 120 Ω
2. V_ab = −0.06818 V
3. I_g = −1228 µA
4. R_th = 148.9 Ω
5. V_o = 1.537 mV
6. V_o = 7.5 mV

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