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

In the bridge shown, V_s = 3 V, R₁ = 1000 Ω and R₂ = 300 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 3 VR₁ = 1000 ΩR₂ = 300 ΩR₃ = 60 ΩR₄ = 10 Ω

V_a = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 800 Ω, R₂ = 600 Ω and R₃ = 100 Ω. Find the unknown resistor R₄.

R₁ = 800 ΩR₂ = 600 ΩR₃ = 100 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 = 12 VR₁ = 150 ΩR₂ = 150 ΩR₃ = 120 ΩR₄ = 100 Ω

R_th = Ω

4.Medium

A bridge has four 300 Ω arms and V_s = 12 V. The sensor R₂ increases by ΔR = 0.6 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 12 VR = 300 ΩΔR = 0.6 Ω

V_ab = mV

5.Hard

A quarter bridge with one active gauge (GF = 2.12) is excited with 3 V. Under load the output reads 1.908 mV. Find the strain ε in µε.

V_s = 3 VGF = 2.12V_o = 1.908 mV

ε = µε

6.Hard

A bridge with 350 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1200 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2ε = 1200 µε

V_o = mV

Answer key

1. V_a = 0.6923 V
2. R₄ = 75 Ω
3. R_th = 129.5 Ω
4. V_ab = 6 mV
5. ε = 1200 µε
6. V_o = 1.5 mV

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