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 bridge shown is supplied with V_s = 3 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 3 VR₁ = 120 ΩR₂ = 600 ΩR₃ = 20 ΩR₄ = 300 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 200 Ω, R₂ = 250 Ω and R₃ = 500 Ω. Find the unknown resistor R₄.

R₁ = 200 ΩR₂ = 250 ΩR₃ = 500 Ω

R₄ = Ω

3.Medium

A 330 Ω strain gauge is one arm (R₂) of a bridge with four equal 330 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 = 330 Ω

P_g = mW

4.Medium

A bridge has four 470 Ω arms and V_s = 5 V. The sensor R₂ increases by ΔR = 47 Ω. Find the exact output V_ab in mV.

V_s = 5 VR = 470 ΩΔR = 47 Ω

V_ab = mV

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1 mV/V at its rated load of 50 kg. It is excited with 10 V. Find its output V_o under a load of 25 kg.

1 mV/VF_rated = 50 kgV_s = 10 VF = 25 kg

V_o = mV

6.Hard

A strain gauge (GF = 2.05) on a member with E = 110 GPa forms a quarter bridge excited with 10 V. The output reads 6.15 mV. Find the axial stress σ in MPa.

V_s = 10 VGF = 2.05V_o = 6.15 mVE = 110 GPa

σ = MPa

Answer key

1. I_s = 13.54 mA
2. R₄ = 625 Ω
3. P_g = 3.03 mW
4. V_ab = 119 mV
5. V_o = 5 mV
6. σ = 132 MPa

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