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 = 600 Ω, R₂ = 10 Ω and R₄ = 10 Ω. Find the setting R₃.

R₁ = 600 ΩR₂ = 10 ΩR₄ = 10 Ω

R₃ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 800 Ω, R₂ = 200 Ω and R₃ = 600 Ω. Find the unknown resistor R₄.

R₁ = 800 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 = 15 VR₁ = 60 ΩR₂ = 80 ΩR₃ = 80 ΩR₄ = 800 Ω

R_th = Ω

4.Medium

A galvanometer with a resistance of 20 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 = 1000 ΩR₂ = 100 ΩR₃ = 800 ΩR₄ = 1000 ΩR_g = 20 Ω

I_g = µA

5.Hard

A 350 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.14 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2ΔR = 0.14 Ω

ε = µε

6.Hard

A quarter bridge with one active gauge (GF = 2.1) is excited with 10 V. Under load the output reads 1.05 mV. Find the strain ε in µε.

V_s = 10 VGF = 2.1V_o = 1.05 mV

ε = µε

Answer key

1. R₃ = 600 Ω
2. R₄ = 150 Ω
3. R_th = 107 Ω
4. I_g = −1673 µA
5. ε = 200 µε
6. ε = 200 µε

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