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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 3 V.

V_s = 3 VR₁ = 300 ΩR₂ = 300 ΩR₃ = 50 ΩR₄ = 300 Ω

V_ab = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 500 Ω, R₂ = 400 Ω and R₃ = 400 Ω. Find the unknown resistor R₄.

R₁ = 500 ΩR₂ = 400 ΩR₃ = 400 Ω

R₄ = Ω

3.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 10 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 10 VR₁ = 250 ΩR₂ = 500 ΩR₃ = 120 ΩR₄ = 400 ΩR_g = 500 Ω

I_g = µA

4.Medium

A galvanometer with a resistance of 20 Ω is connected between a and b of the bridge shown (V_s = 9 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 9 VR₁ = 100 ΩR₂ = 120 ΩR₃ = 300 ΩR₄ = 250 ΩR_g = 20 Ω

I_g = µA

5.Hard

A strain gauge (GF = 2.1) on a member with E = 210 GPa forms a quarter bridge excited with 10 V. The output reads 2.625 mV. Find the axial stress σ in MPa.

V_s = 10 VGF = 2.1V_o = 2.625 mVE = 210 GPa

σ = MPa

6.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 2.5 V. The largest strain to be measured is 500 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 2.5 VGF = 2ε_max = 500 µεV_FS = 5 V

G =

Answer key

1. V_ab = −1.071 V
2. R₄ = 320 Ω
3. I_g = −1351 µA
4. I_g = 3879 µA
5. σ = 105 MPa
6. G = 8000

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