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 = 250 Ω, R₂ = 400 Ω and R₄ = 80 Ω. Find the setting R₃.

R₁ = 250 ΩR₂ = 400 ΩR₄ = 80 Ω

R₃ = Ω

2.Easy

The bridge shown is supplied with V_s = 9 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 9 VR₁ = 60 ΩR₂ = 120 ΩR₃ = 40 ΩR₄ = 600 Ω

I_s = mA

3.Medium

A 250 Ω strain gauge is one arm (R₂) of a bridge with four equal 250 Ω arms and an excitation of 2 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 2 VR = 250 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 = 2 VR₁ = 300 ΩR₂ = 600 ΩR₃ = 80 ΩR₄ = 300 Ω

R_th = Ω

5.Hard

A strain gauge (GF = 2.12) on a member with E = 110 GPa forms a quarter bridge excited with 2.5 V. The output reads 0.663 mV. Find the axial stress σ in MPa.

V_s = 2.5 VGF = 2.12V_o = 0.663 mVE = 110 GPa

σ = MPa

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1.5 mV/V at its rated load of 100 kg. It is excited with 12 V. Find its output V_o under a load of 60 kg.

1.5 mV/VF_rated = 100 kgV_s = 12 VF = 60 kg

V_o = mV

Answer key

1. R₃ = 50 Ω
2. I_s = 64.06 mA
3. P_g = 4 mW
4. R_th = 263.2 Ω
5. σ = 55.04 MPa
6. V_o = 10.8 mV

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