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 = 20 Ω, R₂ = 40 Ω and R₃ = 60 Ω. Find the unknown resistor R₄.

R₁ = 20 ΩR₂ = 40 ΩR₃ = 60 Ω

R₄ = Ω

2.Easy

In the bridge shown, V_s = 12 V, R₁ = 150 Ω and R₂ = 600 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 12 VR₁ = 150 ΩR₂ = 600 ΩR₃ = 500 ΩR₄ = 60 Ω

V_a = V

3.Medium

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

V_s = 2 VR₁ = 80 ΩR₂ = 100 ΩR₃ = 300 ΩR₄ = 300 Ω

R_th = Ω

4.Medium

A bridge has four 470 Ω arms and V_s = 10 V. The sensor R₂ increases by ΔR = 4.7 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 10 VR = 470 ΩΔR = 4.7 Ω

V_ab = mV

5.Hard

A bridge with 350 Ω arms is excited with 10 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.05 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.05ε = 750 µε

V_o = mV

6.Hard

A bridge with 120 Ω arms is excited with 2.5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.12 and the strain is 250 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.12ε = 250 µε

V_o = mV

Answer key

1. R₄ = 120 Ω
2. V_a = 9.6 V
3. R_th = 194.4 Ω
4. V_ab = 25 mV
5. V_o = 7.688 mV
6. V_o = 1.325 mV

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