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 = 50 Ω, R₂ = 20 Ω and R₃ = 100 Ω. Find the unknown resistor R₄.

R₁ = 50 ΩR₂ = 20 ΩR₃ = 100 Ω

R₄ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 500 Ω, R₂ = 500 Ω and R₄ = 20 Ω. Find the setting R₃.

R₁ = 500 ΩR₂ = 500 ΩR₄ = 20 Ω

R₃ = Ω

3.Medium

A 500 Ω strain gauge is one arm (R₂) of a bridge with four equal 500 Ω arms and an excitation of 10 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 10 VR = 500 Ω

P_g = mW

4.Medium

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

V_s = 9 VR₁ = 120 ΩR₂ = 40 ΩR₃ = 300 ΩR₄ = 1000 Ω

R_th = Ω

5.Hard

A quarter bridge with one active gauge (GF = 2.12) is excited with 2.5 V. Under load the output reads 0.795 mV. Find the strain ε in µε.

V_s = 2.5 VGF = 2.12V_o = 0.795 mV

ε = µε

6.Hard

A quarter bridge with one active gauge (GF = 2.12) is excited with 10 V. Under load the output reads 1.06 mV. Find the strain ε in µε.

V_s = 10 VGF = 2.12V_o = 1.06 mV

ε = µε

Answer key

1. R₄ = 40 Ω
2. R₃ = 20 Ω
3. P_g = 50 mW
4. R_th = 260.8 Ω
5. ε = 600 µε
6. ε = 200 µε

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