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 = 400 ΩR₃ = 100 ΩR₄ = 500 Ω

I_s = mA

2.Easy

In a slide-wire (metre) bridge a known 100 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 30 cm from the left end A of the 100 cm wire. Find R_x.

R = 100 Ωl = 30 cmL = 100 cm

R_x = 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 3 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 3 VR = 330 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 = 9 VR₁ = 50 ΩR₂ = 40 ΩR₃ = 800 ΩR₄ = 50 Ω

R_th = Ω

5.Hard

A bridge with 120 Ω arms is excited with 2.5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.05 and the strain is 600 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.05ε = 600 µε

V_o = mV

6.Hard

A strain gauge (GF = 2.05) on a member with E = 200 GPa forms a quarter bridge excited with 3 V. The output reads 0.922 mV. Find the axial stress σ in MPa.

V_s = 3 VGF = 2.05V_o = 0.922 mVE = 200 GPa

σ = MPa

Answer key

1. I_s = 10.77 mA
2. R_x = 233.3 Ω
3. P_g = 6.818 mW
4. R_th = 69.28 Ω
5. V_o = 1.537 mV
6. σ = 119.9 MPa

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