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

In a slide-wire (metre) bridge a known 2 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 70 cm from the left end A of the 100 cm wire. Find R_x.

R = 2 Ωl = 70 cmL = 100 cm

R_x = Ω

2.Easy

The bridge shown is supplied with V_s = 6 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 6 VR₁ = 20 ΩR₂ = 120 ΩR₃ = 150 ΩR₄ = 1000 Ω

I_s = mA

3.Medium

A bridge has four 200 Ω arms and V_s = 12 V. The sensor R₂ increases by ΔR = 20 Ω. Find the exact output V_ab in mV.

V_s = 12 VR = 200 ΩΔR = 20 Ω

V_ab = mV

4.Medium

A 1000 Ω strain gauge is one arm (R₂) of a bridge with four equal 1000 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 = 1000 Ω

P_g = mW

5.Hard

A quarter bridge with one active gauge (GF = 2.1) is excited with 2.5 V. Under load the output reads 0.656 mV. Find the strain ε in µε.

V_s = 2.5 VGF = 2.1V_o = 0.656 mV

ε = µε

6.Hard

A strain gauge (GF = 2) on a member with E = 210 GPa forms a quarter bridge excited with 2.5 V. The output reads 1.875 mV. Find the axial stress σ in MPa.

V_s = 2.5 VGF = 2V_o = 1.875 mVE = 210 GPa

σ = MPa

Answer key

1. R_x = 0.8571 Ω
2. I_s = 48.07 mA
3. V_ab = 285.7 mV
4. P_g = 2.25 mW
5. ε = 499.8 µε
6. σ = 315 MPa

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