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 = 80 Ω, R₂ = 250 Ω and R₃ = 800 Ω. Find the unknown resistor R₄.

R₁ = 80 ΩR₂ = 250 ΩR₃ = 800 Ω

R₄ = Ω

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 5 V.

V_s = 5 VR₁ = 1000 ΩR₂ = 1000 ΩR₃ = 150 ΩR₄ = 250 Ω

V_ab = V

3.Medium

A 150 Ω strain gauge is one arm (R₂) of a bridge with four equal 150 Ω arms and an excitation of 3 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 3 VR = 150 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 = 3 VR₁ = 150 ΩR₂ = 80 ΩR₃ = 80 ΩR₄ = 600 Ω

R_th = Ω

5.Hard

A strain gauge (GF = 2) on a member with E = 200 GPa forms a quarter bridge excited with 2.5 V. The output reads 0.313 mV. Find the axial stress σ in MPa.

V_s = 2.5 VGF = 2V_o = 0.313 mVE = 200 GPa

σ = MPa

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 200 kg. It is excited with 10 V. Find its output V_o under a load of 50 kg.

2 mV/VF_rated = 200 kgV_s = 10 VF = 50 kg

V_o = mV

Answer key

1. R₄ = 2500 Ω
2. V_ab = −0.625 V
3. P_g = 15 mW
4. R_th = 122.8 Ω
5. σ = 50.08 MPa
6. V_o = 5 mV

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