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 = 500 Ω, R₂ = 200 Ω and R₃ = 1000 Ω. Find the unknown resistor R₄.

R₁ = 500 ΩR₂ = 200 ΩR₃ = 1000 Ω

R₄ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 100 Ω, R₂ = 800 Ω and R₄ = 80 Ω. Find the setting R₃.

R₁ = 100 ΩR₂ = 800 ΩR₄ = 80 Ω

R₃ = Ω

3.Medium

A bridge has four 300 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 45 Ω. Find the exact output V_ab in mV.

V_s = 15 VR = 300 ΩΔR = 45 Ω

V_ab = mV

4.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 3 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 3 VR₁ = 800 ΩR₂ = 40 ΩR₃ = 10 ΩR₄ = 10 ΩR_g = 500 Ω

I_g = µA

5.Hard

A 120 Ω strain gauge with gauge factor 2.12 is bonded to a steel bar. Under load its resistance rises by 0.1908 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.12ΔR = 0.1908 Ω

ε = µε

6.Hard

A quarter bridge (one active gauge, GF = 2.05) is excited with 2.5 V. The largest strain to be measured is 750 µε, and it must give 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 2.5 VGF = 2.05ε_max = 750 µεV_FS = 2.5 V

G =

Answer key

1. R₄ = 400 Ω
2. R₃ = 10 Ω
3. V_ab = 523.3 mV
4. I_g = −2499 µA
5. ε = 750 µε
6. G = 2602

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