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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 3 V.

V_s = 3 VR₁ = 800 ΩR₂ = 200 ΩR₃ = 400 ΩR₄ = 400 Ω

V_ab = V

2.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 20 cm from the left end A of the 100 cm wire. Find R_x.

R = 2 Ωl = 20 cmL = 100 cm

R_x = Ω

3.Medium

A bridge has four 500 Ω arms and V_s = 9 V. The sensor R₂ increases by ΔR = 40 Ω. Find the exact output V_ab in mV.

V_s = 9 VR = 500 ΩΔR = 40 Ω

V_ab = mV

4.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 12 VR₁ = 80 ΩR₂ = 800 ΩR₃ = 600 ΩR₄ = 100 Ω

R_th = Ω

5.Hard

A strain gauge (GF = 2.05) on a member with E = 210 GPa forms a quarter bridge excited with 2.5 V. The output reads 0.256 mV. Find the axial stress σ in MPa.

V_s = 2.5 VGF = 2.05V_o = 0.256 mVE = 210 GPa

σ = MPa

6.Hard

A bridge with 120 Ω arms is excited with 5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2 and the strain is 600 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2ε = 600 µε

V_o = mV

Answer key

1. V_ab = −0.9 V
2. R_x = 8 Ω
3. V_ab = 173.1 mV
4. R_th = 158.4 Ω
5. σ = 41.96 MPa
6. V_o = 3 mV

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