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 = 200 Ω, R₂ = 400 Ω and R₄ = 250 Ω. Find the setting R₃.

R₁ = 200 ΩR₂ = 400 ΩR₄ = 250 Ω

R₃ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 500 Ω, R₂ = 200 Ω and R₃ = 600 Ω. Find the unknown resistor R₄.

R₁ = 500 ΩR₂ = 200 ΩR₃ = 600 Ω

R₄ = Ω

3.Medium

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

V_s = 2 VR₁ = 40 ΩR₂ = 250 ΩR₃ = 60 ΩR₄ = 40 Ω

R_th = Ω

4.Medium

A bridge has four 200 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 10 Ω. Find the exact output V_ab in mV.

V_s = 15 VR = 200 ΩΔR = 10 Ω

V_ab = mV

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1 mV/V at its rated load of 50 kg. It is excited with 10 V. Find its output V_o under a load of 20 kg.

1 mV/VF_rated = 50 kgV_s = 10 VF = 20 kg

V_o = mV

6.Hard

A bridge with 120 Ω arms is excited with 5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.05 and the strain is 200 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2.05ε = 200 µε

V_o = mV

Answer key

1. R₃ = 125 Ω
2. R₄ = 240 Ω
3. R_th = 58.48 Ω
4. V_ab = 182.9 mV
5. V_o = 4 mV
6. V_o = 2.05 mV

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